This design is a bit unorthodox but worked well and has EGR provisions. Would run great with a big block TBi on an adapter.
...

The LT1 cam is plenty mild. I ran one on a stock tune for close to a year in my G20 van without issues. Ran well on the stock van ECM even better on a 1993 Cop Car ECM. If you have the clearance...

My suggestion was more along the lines of selecting that application to get a rebuild kit with pistons included. LT1 pistons are fairly lightweight and the balance will be off pretty bad. A 305...

1991 B-car like a Caprice or Cadillac L05 should be flat top.