many thanks. I'm gonna check my squish clearance this WE. Got plenty of head gaskets but need to oversize them to 67,5mm( from 66,5) to proceed to the checking.
rebuilding on its way:
gearbox reassembled, perfect play (0,04mm), everything seems to just fit perfectly. My previous grinding op of the layshaft has produced its results: Now the big shim rests on the 1st gear and leaves free the layshaft.