so I’ve read around a bit on timing. I know these engines with the stock carb were about 8° BTDC. I know that when you change carbs and fuel characteristics you should change timing.

What timing would you sugest to start with.
I’ve also heard of a technique going off of vacuum inplace of a light

Ive got some engine vibration a partial throttle and load but once it’s wide open it’s smooth as day.

Have to read up and study on ignition timing. The initial or base timing number isn't really that important by itself. What you're interested in, is the entire timing curve from idle thru high rpm. If you can't make changes to the internal mechanism, you're very much limited to what you can do with the initial timing anyway. Too little and performance and efficiency suffers. Too much and it will rattle and ping.

The stock OEM timing curve is slow and conservative which makes sense in a heavy truck designed to haul heavier loads. By now it's possible too a rebuilt or remanufactured distributor has been installed, for a completely different application.

The trick way of course is to have the distributor checked out and curved on a distributor machine. You can do this yourself, on the engine, but it is tedious. The first thing I'd recommend is verify that TDC is marked accurately on the crankshaft damper using a piston stop tool. This is the baseline for everything. It is not uncommon for defective dampers to throw everything off, original crankshaft dampers are usually if not always toast by now.

Then map out what the distributor is doing from idle to say 4000 RPM or so, in 500 RPM increments. Look to see that the mechanical advance moves smoothly, up and down. Everybody usually says to get a dial-back timing light, they are cool, but they sometimes have trouble with electronic or high output ignition. I use a basic, inexpensive light that runs on 2 D cells, keeps the rats nest of wires and cables down a little bit when doing tune-ups.

Summit, JEGS and Speedy and the other usual suspects sell flourescent timing tape with marks going out to 50° BTDC, these are a lot easier to read. Also check that the distributor itself is not worn out. They get loosey goosey and wobble, breaker plate sticks and the dwell and timing is erratic.

FE forum? Still new to FTE