If your truck is performing as you describe, why would you even consider a swap regardless of cost? That kind of performance from a 75 year old truck is excellent. How much faster would you want to drive it, anyway? It wasn't designed to travel any faster than you're already going in the first place.
My truck, without overdrive, cruises between 55 and 65 with no real effort. I have gotten it up to 70 once but that is the absolute limit, I think. I don't feel the need to drive it any faster than that.
If your engine blows up, then start looking for a 235 unless a running 216 falls in your lap. That's my plan.
