We've changed the front oil seal on 4.9L with the powertrain dropped down and out. Its easy to have success if you work carefully and deliberately. Its a pretty big job as the front cover also supports the water pump and the hose feed housing below for the coolant. Autozone has a harmonic balancer puller loaner with the correct threaded insert. The front cover gasket set will have the oil seal, cover, water pump and water feed housing gaskets. Make note of all of the 20 or so bolts and nut locations that hold the cover, feed housing and water pump in place. Follow the torque settings very carefully. SOme of the bolts and nuts are small 10MM and it doesn't take much to strip them. Remember to drain the coolant before starting or you will end up with it in the oil pan.
While you may be able to do the job with the engine in place, I would not attempt do it that way. There is just so little room to work in that area.
------------------ " THE BLACK PARALYZER"
-87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 06-07-2015).]