Forgot to mention that yes, you can use an HEI distributor with the older 235's. I used a HEI from a 1975 Pontiac Firebird with a 250 I had lying around. I wired it up to a relay. The truck's wire that goes to the coil puts out about 9v. I have learned from trial and error that 9v is enough to trigger and hold the 12v Bosch relay. So I took that wire from the coil and used it as the trigger for the relay. So if anyone in the future is unsure of what to do, now you do not have to go chase down an ignition source wire
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