You do generate a bit of heat when you're reshaping metal.
Mine did not get that far but the gears had started to deform enough to make the box noisy. That box in the pic above must have let out some warning noises before it got to the stage where there was no drive through the indirect gears.
I can't tell you if your rangie box will fit but I suspect not. The bell housing and input shafts I think are different lengths. At least that is the case with Disco V8 and Tdi boxes.
I think you could get an input shaft and laygear for a couple hundred from the UK.
FTC4980 LAYSHAFT | shop | www.lrseries.com | L. R. Series
FTC4982 LAYSHAFT R380 SUFFIX J | shop | www.lrseries.com | L. R. Series
the input pinion is about 150 GBP
The L suffix did not come out in the D1 so you might have to go and have a word to Fred and see what mix of parts you need.
You may be able to pick up a second hand box for about the same price but it could be a lottery.