71 C10 454 Engine Swap Info needed

[Hack71]

I'm preparing for an engine swap on my 71 C10 Cheyenne long box. The truck is an original 350/TH350 with factory A/C, PS, PB, I will be swapping in a 454/TH400 from a motorhome. I want to be as prepared as possible. I've searched some posts and got some conflicting info. I want to do a budget friendly swap; my biggest concern is how the 454 will sit in the engine bay. I've heard that it depends on which engine frame mounts I use, I would like to use clam style engine mounts and frame towers from a 73 and newer, does it matter if they are from a c10, c20, c30, does it matter if they are from a SBC or a BBC, I've read that the engine could sit to far back on the firewall. I have the transmission yoke for the TH400, Will the 454/400 swap in without changing the length of the driveshaft? Currently I have a two-piece shaft. Will the trans crossmember need to be moved? my plan is to use a 19" electric fan from a Jeep Cherokee and mount it in the 71's original fan shroud. the truck has a 4-row radiator that should be sufficient. Pics are attached, any advice or info would be greatly appreciated. Thanks,