Crowejam, SM465 and 420 have the same bolt pattern, SM420 bearing retainer is smaller than the 465. Jerry was thinking you had a closed-shaft 420 in which case, the bolt pattern would already be correct for the 465 so all you would need to do would be open up the center bore in the bellhousing. The last half of his post, he said to scratch the above advice, meaning that you can't go with a 420 or 465 without going to a newer style truck bellhousing and crossmember.
