My 73 Mach 1 had a 351C. I thought that was the standard engine for a Mach 1. I never heard of the 302 interceptor engine either. I thoght they used the biggest available engine as the base for the interceptor. My 69 Ford Police car had a 427 interceptor.
If you have the heads off you can measure the bore and stroke.
302 =4.00 bore 3.00 stroke compression ratio is 8.4
351 =4.00 bore 3.50 stroke compression ratio is 8.0 or 8.3
400 =4.00 bore 4.00 stroke compression ratio is 8.0
I found HP ratings from 122 to 135 HP for the 302s depending on year of manufacture.
Post your numbers so we can research it.