G'day David,
Here's the maths that should get you close:
Draw weight at your length plus five = about 38 (roughly nominal at subtract three for every inch, although Craig often goes two or three pounds over) plus 5 = 43.
Then subtract five pounds if you are wanting to shoot a 27" back-of-point to valley-of-nock arrow = back to 38.
If it were centre-cut or past, you'd add five, but it's not, so just leave it at 38.
If you want to use a modern, low-stretch string, add another five; if not, just leave it.
If you want to shoot 125 grain points, just leave it. If you want to shoot 145 to 160 grain points, add another five. If you want to shoot up to 200 grain points, then add ten. I'd reckon that if you wanted to shoot over 200 grain points to add fifteen to 38.
This should at least give you a starting point if you want to order a test kit with a bit of a spine range, which of course can be tinkered with further by point weight and arrow length. If you can tell us the arrow length, string type and point weight, we can check the maths for you.