There are already TBI retrofit kits on the market (and have been for quite some time) for your Buick. Worse case scenario take the tank out of a 91 Caprice with fuel injection. I believe the tank should fit without modification.
Many times I've thought about converting my Buick to fuel injection. I guess the best way to do it (in my case) is to buy a 1987 Regal parts car. The tank was different. FI cars came with a special anti-slosh tank. If you retrofit an older tank the vehicle will start to sputter ~ 1/4 -1/8 tank. Holley (and others) also make a retrofit FI kit for those cars. In your case, unless buying a FI parts car, go for the Holley TBI kit, and a fuel tank from a 91 Caprice.
A very good reference document is the work done by the EPA on hydraulic hybrids. Google "EPA Hydraulic Hybrids" if you want some extensive research.
Powertrain improvements that allow the engine to be disconnected from the drivetrain, Parallel Hydraulic Hybrid configurations are projected to improve efficiency by 80% with engine off at any time unless storage regeneration is provided by the powerplant.
Their 2006 document included projections of 66 MPG in local driving and 50 MPG highway for a 7400 pound class 2 truck with a frontal area of 3.7 meters and a CD of .32-.34. Engine efficiency for that configuration was listed at 42% which is right at the top of the best efficiency for current diesels.
Portion of document attached.
Yeah, the hydraulic hybrid ideas rock. I keep waiting for something more to become of it, but it never happens. Seems like it could be incorporated into bigger things like tractors for pulling trailers, etc.
HC, the only problem I see is that the tank from an Astro or S10 isn't compatible w/o modification. (If I remember correctly your model car has the fuel filler in the rear behind the license tag.) A 91 Caprice has the exact same configuration.