Hi,
I've always found swapping to a different engine/tranny brand causes more problems than you ever envisage at the start.

I've done the swap from B18 to B20 with O/D and it's a straight drop in. Changing your car to run the FI isn't entirely simple (not too impossible either) but there is no need. Just pull off all the FI stuff down to and including the manifold. I assume you have a onepiece inlet and exhaust manifold, so you'll need to get one of the Volvo aluminium inlet manifolds and bolt on your twin SUs. You keep the FI exhaust manifold. Put your old fuel pump from the B18 on the B20, hook everything up and away you go. You will probably have to change the needles in the SUs, but all pretty simple.

I'm not sure about prop shafts and gearbox lengths, but I think the M41 and the auto box were about the same length and used the same cross-member mounting points. Either way, a fairly simple fabrication job.

You'll need a new propshaft to get the right length. The 240 shaft gearbox flange will be bigger than that on your current shaft, so drop in the new engine and box, measure the distance betweent the gearbox flange and the diff flange carefully - about 3 times to be sure - and take both shafts (from the 240 and 122) to the local prop shop and get them to make up exactly what you want.

Have a great time with it, and remember to check everything several times before committing to it!

Regards

John