There is an entire WORLD of aftermarket parts for those 350 small blocks they've been making them since the dawn of time and guys use them for everything including high horse power race motors so there's a literal universe of parts out there. Since you mentioned it Check out Engine Masters, Road Kill, Roadkill Garage(motor trend in general) and just see what they use. I don't own a car like that and I'm not super into old car so idk all the brands and stuff but it can't be hard to find out. Just google and check those Youtube chan especially Engine Masters. They have multiple videos on modding 350's and talking all about them and David Freiburger of Roadkill, Steve Dulcich of Engine Masters magazine and Steve Brule of Westech Performance Group are basically the GODS of 350's and all those old school cars and engines.