I'm thinking no easy way on the stock tranny unless he replaces it with the later design. I think the easiest is to dive into the stock third member and do a ring and pinion change to a 3.55. Today, I am buying a complete torque tube and rear axle assembly to do just this. Do a ring and pinion/bearing change in advance and get it all buttoned up then do the exchange in an afternoon. Used torque tube rear end assemblies you can get for at the most $25 some are free.

Last edited by sstock; 04/13/2018 2:34 PM.
1953 Chevrolet 3100
261 cu inch, sm420, 3.55 rear, torque tube still,omaha orange, still 6 volt, RPO green glass, side carrier spare, all done
In the DITY Gallery
Video of the 261 running

1964 GMC 1000
305 Big Block V6, sm420, the next cab off restoration