Don't even need the degree wheel if you do it this way -- although you probably have it installed to roll the cam at the same time during the assembly.
Here's a chart that will help:
Flathead Ign. Timing:
2.437 stroke, 3.875 rod length
.148 25.0
.160 26.0
.172 27.0
.185 28.0
.198 29.0
.212 30.0
.225 31.0
.239 32.0
.254 33.0
.268 34.0
.284 35.0
If you want the timing set at 30*, then align your reference marks for timing when the piston is @ .212" BTDC.