Lock up would definitely be prefered, but if the motor makes anything over 80hp, you'll need one.
Definitely OEM stator, or race tech. Just google "Rickey stator bansheehq"
A round house swinger is way easier to adjust and keep it right.
Maier is definitely hit or miss. There are a lot of really cool aftermarket companies. Full bore is making another run. That would be ideal. If not there are a lot of really nice aftermarket hoods out but no many options out back. Otherwise there is a lot of nice used stock stuff.
Only buy second hand motors that are very well documented. Sprink's is a good example.
If you don't wanna do all the assemble it, it maybe in your best interest to have a builder do it for you. There are a few who get motors shipped properly and headache free.