I'll try and answer a few of your ifs'.
Power steering, look for any 194/230/250 in the wrecking yard with power steering. You want all the pulleys, brackets, and pump. You do not want anything from an integral (intake manifold is part of head) head six or a 292 six. I've got a bin full power steering brackets that are not complete sets.
Alternator?? you should have one now.
Automatic with overdrive, I'm not much on automatics, but you should be able to get away with a 200R4 or 700R4 depending on how many horses your daily driver is going to have. Floor shift your choice. You will need a cross member to mount the reart of the tranny and a bracket on the carb throttle shaft to hook the cable from the tranny to.
250 performance how much? Sixes are not cheap to build especially the more ponies you want. The good news is that a 307 v8 piston will swap with the 250 and up your compression. Since the 307 was not a popular motor there are some forged 307 piston from the likes of TRW still floating around, saves a bunch over custom. I suggest you do a search on inliners.org I couldn't find the post but tlowe did a series of dyno runs on the 250 with an assortment of carbs, cams, and head work between 3/16/10 - 4/5/10.
That's a start.
Larry
