I have an A833 bolted up to Chevy bell housing that had a SM465 on it. It was a tight fit, but the input bearing for the 465 is larger than the SM420. They did make a special bell housing with the both Chevy and Mopar bolt pattern on it, scarce.
Since you don't have the shifter, I'll assume you don't have the plate the shifter bolted too. If you can get the original distributer do so, it will save a lot of hassle. The original plate for that transmission is bent over the top of the tail shaft, putting the shifter top center. Bolting a Hurst to it could have the reverse lever banging the mounting bolts. Finding a Hurst for a Muncie, Saginaw, or ?? with mounting plate and shift rods at least one maybe more problems. First I'm not sure the three bolt pattern on the Muncie and Saginaws is the same as the A833. The plate is straigth up moving the shifter about 1-2 inches towards the driver. For sure the shift rod lenghts are different, longer. Mopar used the A833 behind everything from the slant six to the Hemi, and in everything from the Duster to the Vans. Even though they were use in everything the Mopar crowd thinks the shifters are worth their weight in gold. If you can find a shifter out of a Dodge van (even the 3/4 ton) you will have the right lenght rods and shift knob will be about the right hieght. The mounting plate is flat like the Muncie and Saginaws.
Larry
