Huke Basart still sells the bellhousings but if you gonna swap the whole motor+trans you won't need it. You will need to do a lot of other mods tho, think of motor mounts, tunnel modification, driveshaft, coolant tubes and radiator, it's not a carb motor you will need a electric inline fuel pump and return line, exhaust piping, check if the trans has a speedo drive, temp gauge and sensor from a B18/20 can not be used, you will need to convert to electric gauge, electric cool fan (there will be not enough clearance for the mechanical fan), etc... P?rsonaly i think it is WAY easier to prep a B20, they can make lot more power than a stock B19E
edit:
reading trough the 10 year old topic again, i got to have this of my chest for anyone thinking to put a M41 behind a powered motor knowing it's gonna blow, it is such a waste. Prices for this boxes in good condition ar nowadays tripled compared to 10 years ago.