Twin turbo: 318 or 360, and why? This are your only options. GO!
The base motor is the only stricture. How you build it is up to you
Oh well then I'll tell you my dream;
A staged kit with a big remote.
Two tiny ones, not twins; one stuck in up in each fenderwell with the exits coupled to valved bypasses, that then spool up the remote. The cold side plumbed to the primaries of a spreadbore, with small tubes. The remote coldside plumbed to cover the entire airhorn with a pressure balance to the primaries.
The front turbos are sized to work right off idle and be done sometime after cruising speed, say 2800.
The remote is sized to be ready to begin about there and power up the topend.
Who cares what size SBM you use with this set-up, the fronts are already making 360HO torque, rpm for rpm. I'd probably start with a cheap to replace heavy-rod 318 with a steel crank. I'd try to hide the cold pipes in the cowl and pressurize a modified 14" OEM type air filter house. You'll have to look carefully to find the turbos.
If I had to, I would sacrifice the rear seat, cuz nobody has been there in ~16 years. The seat has not even been in the car since 2004.
I would try to run it with no mufflers.
I would switch to an automatic. And start with 2.94 gears, for 65~2300rpm. That means I would have to run the standard 727 ratios to hit 60=5450.... still in first gear. And that means an easy-on-the-fuel cam, and a remote dial-a-pressure;maybe.
I'd try it with about a 2200stall.
I hate BOVs
Although I do have a 273 block, and a steel 318 crank,hmmmmmmmmmmm;
oh sorry 273 was not on the list,lol.
I didn't vote yet
Ok then;I could make it small-valve 360 heads, onto a 318,with maybe a 360 cam, I think I got a couple of those around here somewhere........
I'd be happy with about 440/350, cuz a fun streeter don't need a lot of horsepower, but with a stinking automatic, it does need a wide torque band, that starts right at stall.
