4.9 instead of 4.5??

Funds??? It should not be a costly conversion. Check out the wrecking yards in your local area. A wrecking yard near my area will sell me a 4.9 for $80. If the engine has less than 150k miles, I would not bother to rebuild it. These are very long lasting engines. If more than 150k miles, I might replace the piston rings. The other thing to note is whether or not the 4.9 heads will adapt to the 4.5 intake manifold that you would use. I believe that it works with some modifications to get the water ports to line up. I can look this up for you if you would like. Send me a Private Message if you're interested and I'll also forward you a article that explains all the differences between the heads and intake manifolds. The other expense would be the adjustable FPR which is not expensive. But the most expense will be time and labor.

By the way, what is wrong with your 4.5? My 88 eldorado also has this engine and at 240k miles and it still chugs along fine. I waiting for it to bite the dust so I can also do the 4.9 conversion but I bet it'll get 300k before it needs attention. It would be neat to have a 4.9 with TBI in this car because the TBI system is so much simpler. I only have to worry about 2 injectors that rarely clogs up rather than 8. Also, my car has the rare astroroof and I have also installed the touring suspension which includes sway bars and a fast ratio steering rack. The pearl blue custom paint job makes it a sweet ride.

Your 88 Fleetwood would be a good candidate for the 4.9 since the newer Fleetwoods got much larger. The styling on the 87/88 FWD Devilles/Fleetwoods is also very sweet.