TH400 into '62 C10

[Middleagecrisis]

I'm getting ready to slip my fresh 327/TH400 (shorttail) transmission in my '62. The truck came with a worn out TH350 (shorttail also). My question concerns the trans mount and what needs to be done to make the TH400 fit. Moving the crossmmeber further back on the frame isn't an option, as the frame narrows where the crossmember attaches, so it all stays in the factory location. It looks like the PO elongated the factory crossmember mount holes. I'm sure a TH400 has been swapped in these trucks in the past. The trans may set on the crossmmeber just fine, I haven't tried mocking it up yet. I'm going to slip the motor/trans in on Monday and am curious what to expect. I have the correct trans yoke and know the driveshaft may need to be shortened. I'm also running an aftermarket rachet shifter, so shifter mods are not a concern.