Everyone that has mentioned the 4.9L swap seems to not fully understand these engines.
I actually own a 1991 Cadillac Seville with this engine in it. The fuel economy in it isn't amazing, usually getting around 15-18MPG in the city. My car does have 194,000 miles on it but at the same time it's been HELL to make it run the right way. As far as price it seems to be right around the same as a 3.8SC swap.
From the sound of it, it seems like a 3.8SC swap is out of the question for you because it's hard to find in your area.
I would definitely look into just doing a 3.4PR engine, mainly because of the cost but they are really easy to swap, and you'll have enough money left over to bore the engine, turbo or supercharge if you wanted to. The output won't be neck breaking but it will add a good amount of horsepower for the cost.
But in the end, it's all up to you.
The wetter the better