A couple of weeks ago I helped a friend with an engine installlation where he had the same problem. It was a the tube for the throw out bearing (late model) that was bent.
A type 3 trans fits in a type one with minor changes:
1: The hole for the shift tube on the hockey stick is down on a type3 and up on a type 1. You can just change them, it is easier than drilling a new hole.
2: There is no holes for the rear tranny mounts. You can easily drill them, it is magnesium.
i suspect the tube as well as i can shake the engine arond a bit, but won't slip over.
the hocky stick is changed, i found that out after fitting the trans the first time...

a lot off ugly words came out off my mouth that day.
just to to make things clear. this is a type1 gearbox in a type3. so the trans has the holes and i have always fitted the nuts from the inside out so interferance would be minimal.
Get a bigger hammer

thought about it, but i was thinking off NOT cutting off the whole arm because off a broken fingernail for once

i will check the fitment off the pressureplate and throwout bearing again, but it all looked OK.
will keep you updated, thanks allready.