I'm not clear on exactly what the problem is, but I fitted an alternator to my 270 recently using the original belt (to keep everything simple) by machining up a C-section pulley and fitting it to the alternator.
I had to weld one new lug onto the original mount bracket to align the alternator,and find a suitable tensioner bracket, but there were no real problems.
I found after I had made the new pulley,that they were available off the shelf in C-section anyway.The only adantage in making it myself was that it could be made a smaller diameter than otherwise available and so keep the rpm of the alternator up, with a relatively low revving engine.
Hope this helps.
