Swapping the 84-87 front end into an 88 is just nuts... The people who liked/raced the 84-87 front/88 rear were running 84-87 Fieros and that is what they knew and were familar with. The 84-87 front suspension is poor at best... the only thing it has going for it its easily rebuild-able wheel bearings. Every other aspect is a step backwards.
Converting the stock 88 upright to a spindle is problematic from a packaging standpoint because the face of the hub is 1.4" from the upright. The spindle hub for the 84-87 is 3.5" deep. You can't push the wheel flange out w/o a widebody and you can't extend the hub portion either as it would stick out past the wheel. What makes the spindle setup stronger (bearings last longer) is the distance between the two races of the bearings, but that also makes it nearly impossible to adapt to the 88. To get a spindle style setup on the front of an 88, you will need to either swap uprights or have a custom one made.
You can "adapt" the rear wheel bearing to the front of an 88. That makes the bearing much cheaper and the rear bearing is stronger, the only downside is it shifts the wheels out .2" because the rear wheel bearings are 1.6" between the upright and hub face.
Another option that has been done is to machine the 88 front wheel bearing housing to accept the bearing guts from a 79-85 rear wheel bearing from the FWD caddys. This hybrid bearing would then be rebuild-able and also has the 5 x 4 3/4 pattern. This has been done once and documented, but finding the "right" hubs to use for the conversion (need to be rebuild-able) has proven hard for others to replicate.
Others have discussed the options of converting the 88 upright to accept other bearings, but so far nothing but discussions have come up.
You can also spend $550 and get a set of dropped uprights that use the rear wheel bearing... then it becomes a bolt on affair and you can level out the ride height of the car... this is probably the best option right now, but their quality control hasn't been the greatest of late. http://www.arrautmotorsports.com/parts/suspensions
If you want larger wheels and plan to track your car, then its all about optimizing the size and weight of the tire/wheel package. Steven Snyder tracks his car quite a bit and runs 17x7 48et and 18x9 45 ET under a stock 88 coupe body. The wheels he uses are available in 5x100mm and cost about $150-$170 each and are decently light. He runs 215/45/17 and 275/35/18 tires. His rear wheel is the widest you can run at the smallest diameter and fit it under a stock body w/o other suspension mods to make more room. Specs on his car are here: http://steventsnyder.com/cars/1988-pontiac-fiero/
So unless you want to run 19's or larger, changing the bolt pattern to get cheap wheels for true performance needs is no longer required.
As you look at brake upgrade options. There are several things to keep in mind.
If you want to maximize track performance, you want to keep weight (both unsprung and rotating) at a minimum. The C4 12" rotor is the absolute best bang for the $$$. You get an additional 1 1/2" in diameter for improved mechanical advantage and heat dissipation for about 3lbs of rotor weight per corner. It also retains the complete 88 brake brake system hydraulics so bias remains stock, parking brake works, and you don't have any other parts to have to buy to match the master cylinder/combo valve/calipers as GM did that for you!
As you look at other brake kits using different rotors, check the weight vs. stock 88 and the rotor width. Most rotors in the 12 3/4 to 13" are will add 7 to 10+lbs or more lbs per corner to the weight and if the rotor width isn't 20mm or less, you will have to buy all 4 calipers, likely a master cylinder, and depending on calipers you might not ever be able to dial in the brake bias. My 13" brake kit adds 6-7 lbs/corner, but retains all the stock 88 hydraulics, brake bias and parking brake function.
Getting back to brake bias... If you run staggered width tires (narrower in front) and/or taller rear wheels (to maximize width), you will need MORE rear brake bias. Part of this is because the rear tires are wider, part of this is the mechanical advantage of the rear is also less due to the taller diameter of the tire. If you don't add more rear bias, you will tend to overheat the front brakes as they will be working much harder than they would if the rears were doing all they could. Aaron88 used to sell a custom bolt in rear brake bias adjustment for the combo valve that truly increases rear brake bias and it works quite well.
Fieros are rather unique in that GM designed their calipers to be the same size front/rear and used the combination valve to adjust bias. Most cars use the piston diameters to make course bias adjustments and then fine tune it with the combination valve. These cars with different size calipers almost always have calipers with smaller piston bores in the rear which = less braking. Most off the shelf brake bias adjusters work to reduce rear braking... so use a rear caliper with a smaller bore than the front and you will not be able to restore the rear bias back to stock, or even raise it like needed for true track duty. Be careful mixing/matching brake system components as you can easily end up with a kit that doesn't perform as well as the other properly designed brake kits.
For the 88's there are 12" and 13" brake kits available from several vendors that are quite economical ($450+ - depending on kit and vendor) that offer significant braking/heat dissipation gains, while keeping the stock 88 Fiero hydraulic system, brake bias and parking brake function.
Products: 88 13" Brake Kit
, 88 12" Brake Kit
, 88 Lateral Link Relocation
, 84-87 Machined Front Hubs
, Custom Machining
, Ramjet SBC/Getrag
, Carb SBC/Isuzu
[This message has been edited by fieroguru (edited 09-14-2014).]