the onan twin from that time frame most likely would have been a BF engine.
the stock points box assy. was 160-1158.
points were R/R and adjusted from the rear.
one of the BF options, was a top adj. points box.
you could adjust point setting/timing while the engine is running.
the stock set up is a P.I.A. on many applications.
if any one is interested i have the GOOD ones ava. for sale.
e/mail or call 651 437 2826 thank you. boomer( the used onan engine parts guy )