1972 Dodge Colt

Finding a stock head in my garage is a challenge.
Almost as hard as finding a Virtuous Lady in a Dallas Gentleman's Club.

However, very unscientific measurement.
2121476-1, 3.60. This is the oldest head I have ever seen, predates Hyper Pak intake by 8422 numbers.
2206035-3, 3.39.
.2 just for argument.

To reduce the chamber volume one cc., mill the head .0063".
If the race head was at 60 CC and it's now at 30 CC then the cut would have been .189.

So it just might be cut that much.