Distributor recurve for tradesman van

Depends on what is in there NOW. The stock advance in ANY "smogger" after about 70-ish and worse after 71-72-ish is very long and very slow, designed for very low numbers initial and doesn't reach full until quite high RPM. WHAT THIS MEANS is that if you start advancing the initial, it can seriously over-advance at high RPM
1....Determine "what is there" diagram it with a timing light and tach
2....If it's a smogger, either weld up the slots and shorten them, or get an FPO limiter plate or kit
3....Experiment with initial timing to determine idle/ off idle/ low RPM in gear
4....Experiment with mid range same way, set timing at RPM for "mid" cruise, IE about 35mph or something
5....Same on top end

You can do this pretty quickly if you degree the wheel, and have a light and tach, and can find some fairly low traveled road, like a straight stretch of county road where you can do 45-50 for a short time.