Trans slow to pickup in AM in Winter is usually sign of hard seals....
I would put a full overhaul kit in it...and new convertor...
Re the engine rebuild...I would be worried about the root cause of the crank breaking...if it has spun a main bearing in that block you may as well use it as a boat anchor....
I build quite a few engines...4 so far this year...and none were flat tappet cam engines...I have two more in process right now...one roller and one flat cam 327 original build...(hence my WTB recently for a 2BBL carb...I have one on the way )
I buy Vortec cores from salvage yards or craigslist,,,usually throw new heads on, depends on what the client wants, and always hot run test each engine before installing...I firmly believe the flat tappet cam engines can be built to last, but once you build a roller you will wonder why it took you so long to try.
The SBC will never give the performance and fuel efficiency of the LS variants, but I do prefer the semi authentic look of a Vortec 350.
Just this old dudes opinion...anyhoo...
