Get an engine from a 90s Fleetwood,Caprice,or Roadmaster. Since they are computer controlled youll need to get an aftermarket carb,distributor,intake manifold,and transmission control module [ if you get the tranny] .These parts can also come off an old pre-80s 350 engine.And use the mounts from the car you got the engine from.You can also use the engine out of a 86-89 fleetwood,but thats an Olds engine.Really any small chevy will do but if you use one from one of the cars above,you can use the mounts,fan shroud,ect and itll look almost factory and go in with no driveshaft work. I HEARD that the 4100 ht caddies had a universal tranny.I never even looked when I swapped mine I needed a tranny too. Also take out the ECM the car will have a constant drain on the battery if you dont.