Which bellhousing?

Ok so from what I'm understanding I need to get a '70 BB aluminum housing, which would have a 4.80 hole, and then have my bearing retainer turned down from 5.125 to 4.80?

I would get a quick time housing if I could afford it but I just don't have $500 for this. I can afford $200 or so for a factory bell but that's about my limit.