My mechanic put a chipped 8v TS into a 2000 105 (1973)- and though there isnt much room, Ive looked at doing the same with a spare TS I have.
Fits straight onto the mounts, and bellhousing can be adapted fairly easily. Gearbox and diff will need work if they want to take much more torque, though. I looked at getting a four link rear end made up- pricey, but with something like a 28 spline Hilux diff (Toyota utitility) under there, 400hp could be feasible with a turbo TS. You also get the better weight distribution of a four cylinder.
The V6 will require a bit of work to get in there, as you will likely know.
That should work.
Using an Alfasei setup and taking it out to 3.3 with Cosworth pistons and liners. I personally, would prefer injection, but each to their own.
This is the sort of six throttle injection setup I would like to do on my 2.5. Its current spec, new ecu with 6 coils (direct fire) and this, should see me crack the 300hp mark. But I didnt pay for the buildup of my motor, so Im not too afraid to spend a little more on it!
The 2.5 apparently weighed in @ 12kgs more than a Nord 2.0, but its sump and sitting position mean that that 12kgs is lower in the chassis, making it prone to understeer. The best way to get rid of understeer IMO is more power!
Definitely 2.0 Turbo.
You could get an 8v TS running stock compression (I dont recommend it though), find a 200SX/SR20 turbo, and pump 10psi into it max, with a decent intercooler, and proper aftermarket injection (dont even think about trying to get the Motronic to run it... not worth the risk), fuel system upgrades... etc. You would have a smidgen over 220hp but the torque would break the rears away under throttle.
Or you could go hi comp, cams, quad throttle bodies, and have an angry TS with around 170-180hp... I like hairdryers though