Okay firstly the engine to vehicle combo is like using a lawnmower for a drag event. The B series engines are massively underpowered to suit any modern applications. The oldest people tend to go is for a 13BT but even thats lost its modjo. I could tell you to get your diff custom built but hey, when you find fnd a guy who can do it, lemme know to The best i can advise you is to use the diff from the LC, obviously fabricated to fit.
As far as V8s go, I dunno of any for sale but i do have a pristine 3-F 4.0 6Cyl (FJ80) motor for sale if you're inetersted(engine only). Its never been rebuilt, absolutly no faults and with a guarenteed 60,000click used. If you're interested, lemme know.
Oh yeah going for 35,000(all ancilliaries inclusive)