First the bad news.....then the other bad news....... then the fall back position.

Spent all day lugging 3 different SM 420 around....... heavy little chunk of steel....so we reverted to using a two wheel lifting dolly...... then lugging in the different Bell Housing some 1940 for the 216 qand some for the 1954 with 235 and the one and ONLY right hand drive hydraulics to the work table.....and .....

Bad news....... the bolt pattern of the SM 420 ( all of them that I have) are totally different than what I has assumed....... I was under the impression that 3 of the tranny bolt holes wouldlline up and only one hole on the right hand side was too far out..... but the spread of the 4 holes are different just enough that they willnot fit and too close to weld and redrill.... I least not at my skill level....conclusion is there is no way for me to fit a SM420 onto the bellhousing that fits to a military 1940 bell housing...even if the 1940 bell housing bolts right up to a 261......and

More bad news..... the horn that goes around the input shaft of the SM420 is about a half inch larger than the horn that fits on the 4 speed crash box.... the military bell housing would need to be machined to the larger size and that would seriously weaken the boss that hold the fulcrum shift fork.......

Conclusion no 1....... you cannot safely fit a SM420 onto a 1940 right hand drive bell housing as it will not fit/bolt on....... and would be nearly impossible to redrill for a new pattern without seriously weakening the bell housing.

One further observation relating to possibly redrill the tranny case..... the right hand bolt, to match the 1940 bell houisng hole would be right into the idler shaft of the SM420....

OK for some good news....... the running 235 can be bolted to the and frame and use the 1954 bell housing with the SM420 but the rear motor mount are different from the solid military mount and the civilian rubber mount of 1954...... however.....fabricating newer adapter motor mount are far more feasible.....or swapping the rear engine cross member from the 54 frame to the CMP frame........ but that reduces greatly the value of the finished vehicle for collectors....... but it could work.....and that implies cutting a rght hand window into the 54 bell housing and relocating the fulcrum bolt to the right side....... needs ver precise drilling or better still machining a new 1 inch threaded hole with a shoulder to insure the fulcrum bolt screwed in with an hex key would be at exactly the same depth for the fork.....dicy and leave a rather weak section of bell housing casting......... good news but very iffy in my mind...... and that leaves the short joining drive shaft that links to the transfer case to be shortened about 1 inch.....

Conclusion no 2 ....... bolt the running 1954 engine with the flywheel and clutch pack to the existing 1940 right hand bell housing..... install the 4 speed crash box and get used to double clutching.....and the military motor mount remain a straight bolt in.....and short drive shaft fits.

Beware of parts that look similar and/or the same until you actually physically get down to measuring.......

Final gold plated conclusion...... that 1960-62 GM right hand drive bell housing that I purchased years ago on a lark cheap ...part # 3817816.... that bolts right up to my 261 and is designed to take the SM420 bolt pattern is now so highly prized and valuable that I may store it under my bed!!!!!!

Time consuming but a worth while learning session.

Did I miss an option........ feel free to jump in .......I may have over looked some other solution.......

Bob C.

Bob C.
CMP Heaven
The Hammond Barn