So this is the engine. Is it 1500? and will it be as simple as just changing the gearbox, knocking a hole in the floor and playing with the tailshaft? Maybe buckets and a rubber boot over the hole?? Thanks for the upload tongy.

100% j15 motor 70-75HP
dont bother with the a series the 620 is a heavy car
pull the angle grinder out and take those engine mounts off at the weld
then find a car with an l20b and pull the engine and gearbox out of it

measure the tip of the gearbox of the j15 to the mounts on the j15

then measure the same on the l20b, you want this measurement to match up as close as possible to the j15 measurement
if you cant find one close enough you will have to get your tailshaft shortened

dont even bother with the j15...was too much of a forklift motor...all torque and no go. The only reason why they weigh so much is the steel tray, usually weighs in at 500kgs by itself. Not very hard to change motors and the l series is plentyful, jsut a stocka will be enough for this thing

Yep - its a J15, same thats in mine currently. If you pull up the carpet/vinyl you might have pre cut access point for a shifter, it has a plastic cap on it. If your not keen for an engine swap and just want the floor shifter, take a look here and see if you can mod the selector arm....... That is my suggestion. Then you could just cut/remove the column shifter possibly. If its a paddock basher for the kids to learn to drive in then leave the crappy J15 in until they blow it up! :)

lol good luck blowing it up