I have a 1954 Olds. I put coil-over shocks in place of the old ones. Although it looks like plenty of room, there's little room for error: you need to know your specific 4 bar config. so your traction bars will mount on flush [bolts or welds]? (pre-1955 Chevy kits are non-existent? Have you located a 4 bar kit for your Buick?)

Other thoughts: Getting my large, original-size tires on and off under the rear fender skirts was a trial-and-error process! If you go lower, you'll have smaller tires that will fit under there?

I had a new 3.5" diameter bellytube driveshaft built [from a Silverado] for the wingcap ujoint on my original pinion yoke. Any length over what...57"? will oscillate and self-destruct at smaller diameters!

My smallblock 350 fit in the front ALMOST like it was supposed to be there - with new engine mounts on the frame I made it fit the mount kit parts for a 350 block. I used big mounting pads bolted onto 1/2" steel 90-degree brackets. I installed my frame mounts almost exactly where the old ones went for the 324 c.i. engine. Beforehand, I checked the transmission-to-rear pinion yoke angles to determine the correct height for the engine mounts (parallel ujoint deflection~ identical angles).

Helpful?