6.1 or 6.4?

I’m going to sell my Dart and buy a 77-84 swb Dodge truck. The plan is to swap to a Gen 3 Hemi and 8 speed transmission. 6.1 or SRT 6.4, and why?

Thanks.
We are doing pretty much the same swap in a 76 D-100. It's a 6.4 w/6speed manual. The 6.1s have less power yes, but they also have less stuff to go wrong too, (VVT, adaptive intake runner lenth etc.) all good things until they go wrong.