We had to shorten tailshaft mainly because we used the 120y borg warner diff and 120y auto tailshaft. 1200 Auto tailshaft to H145 should work as long as you use the shorter L series box like stanza 4 speed or R30/SSS Stanza stumpy 5 speed. Suggestion, drop the motor and box in the bay once everything is removed e.g radiator sit it in place as if its mounted by jacking the box up in place and engine still hanging on crane. Hook up the tailshaft and base your mounting points off that as long as its not to far forward and stanza sump will be fine for L16.You can also put a nice long piece of light timber across the guard tops east west to check engine height/bonnet clearance. we dumped stock carb and air cleaner and went with a weber 32/36. Auto tunnel will be fine. Although don't expect the box to come out or go in easy when disconnected from engine.