Thats a great looking truck. Congrats on the find!
Also, that is a single speed rearend, so the ratio is 6.14 I think.
As far as changing engines, if you want to add a 261, than add one. Just be sure to keep the old 216 stored away somewhere just in case.
As Mike B mentioned above about the 4K rpm max rating, I doubt I would ever run a 216 at that, or if I did I wouldn't for very long. I believe 2500-3000K is a much more comfortable number and it won't sound like shes going to explode on you!
Jeff
