Ian,
Sorry mate I just have not ben able to get on the forum this week due to work commitments - the odd fleeting gliumpse on iPhone has been it. I will respond to your PM's, I promise.
Darren's car has the engine right back against the bulkhead as you have positioned it. This means losing the heater airbox and fan, and that the little coolant hose on the rear of the engine becomes a real PITA to get at. Mine is just enough further forward to allow the heater airbox to fit and I can get a hand down the rear of the engine block if I need to. I have the Manta 400 winged sump like you and there are no fouling issues. Sprint engine mounts are used with fabricated brackets to attach to the block.
I am using the Manta gearbox with a cable clutch. The pedal has been modified to accept the cable and the route through the engine bay is fairly straightforward. My clutch is a Cavalier GSi pressure plate with a Carlton 2.0 litre driven plate and release bearing. The prop is a modified bespoke item with the Getrag gearbox collar at the front end, then a UJ and another UJ at the rear. The diff is standard Dolomite Sprint. The gearlever remote control has been modified by usuing a fabricated welded bracket to reposition the stick slightly and to accept the standard Toledo stick and joint so the internal appearance of the car is bog-standard. The gearbox hangs on a fabricated cross member and rear mount.
Part of the problem I have had helping you out is that the car is not here, and has not been for some time. I have been having a vast amount of work done to the car by a friendly garage on a part time basis with me assisting when I can to keep costs under some sort of control. They are also storing the car for me as, since my house move last year, I have nowhere to keep it under cover at all.
I managed to nip over to the garage on Friday to take a couple of snaps of the new water pump, timing belt and tensioner kit, thermostat, etc. The clutch has also been replaced hence my detailed knowledge of the parts comprising it above. You can just about see the nearside engine mount bracket in the first and last pictures and the offside is partially visible in the second picture. Anyhow, I hope this helps.