Welcome to the shop!! Lots of the guys and gals around here run their stock 216's and are perfectly happy with the results. I would think yours would do 55-60 in stock form but to help it along I'd consider a gearing change in the rear end, Patrick's sells a 3:55 ring and pinion set that works well. A tranny with OD such as the T-5, or a 3-speed with OD combo works well too although you'd need to change to an open drive line.

Good luck with your project, and keep us posted.