The newest versions of the 4 cylinder ISB have had displacement increased to 4.5L and offer up to a 185/515 rating in a OTR application. They also weigh in North of 800#'s wet and have a governed speed of 2500RPM.A 4bt into a mini is going to be a bit tight. It will fit, bc i have seen them, but they are over 700 pounds dressed and the last gen 4bt for an automotive application was 170hp and 420 pound feet of torque. That is a 16V common rail motor I believe, so the older motors would not have that much power. I dont know of a way to bolt a yota tranny to a 4bt, or if it will handle the power. Bellhousing is SAE 2 or 3 and some came with GM patterns for manual and auto trannies.
I would rather have the VW motor as its lighter and smaller and you can get the same amount of power out of it as the 4bt (maybe a bit less tq than the CRD version) Mods are available for VW diesels (TDI & PD) to get 250 hp and 400 tq at the crank. Though this will take some $$$, you can do it for sure..
Good luck and keep us posted...