The larger 235 intake valves can be reduced to a slight oversize (vs. the 216 head OD), and the seat completely refreshed without replacing the seats.
For the exhaust, use V8 1.60".
Typically, going up +1/32" to 3/32" will do it. Narrow the seats from inside as normal.
So why do shops install new seats instead?
It requires actual engineering (not common in the last 30 years), and someone has to pay for those machines.
