Here's the deal...You proposed a solid lifter cam, the cam proposed back to you was the same cam in a hydraulic lifter version. Ho Ho Ho!!!

You're in the right ballpark, but they're right, basically any 360 right up until they switched to 5.9 Magnums is going to have pretty low compression. But you have a 3500 stall converter.

Anyway, here's an idea for you. Go to this page,

http://www.compcams.com/Pages/401/dyno-sheets.aspx

and look at the power curves of the hydraulic cams.
I know it's a smallblock chevy, but it's about the same size, and about the same type of head flow. I did a lot of studying a few years ago and actually made graphs of the different curves that I laid over each other. It looked to me at that time that the XE262 gave up almost nothing to the larger cam, and that's what I'd suggest.

I'd also go with a hydraulic lifter cam unless you have a set of 273 adjustable rockers and the right pushrods in your parts bin.

After you get this combination figured out, a pair of Magnum heads would really help. Or, if you love your '71 heads, a set of KB "quench dish" pistons. KB362 would be my choice.
R.