'84 302 to '90 302, what's needed?

No, your about right on everything. The motors are the exact same except the roller cam part which you are addressing. Just double check and make sure both motors are 50 oz imbalance before swapping over the balancer and flywheel.

you might also need the fuel pump eccentric, not sure if they have them on the 90 engine.. I know the 95 engine I have dint have one..

double check the water pump length too..
headers will work fine..

you might just swap the dist. out for one from an 85 4v .. the 84 dist is probably pretty worn.. might look at an aftermarket or a rebuilt one..