gas?

[Hank70SS]

This is your 3rd post asking about your 1970 Chevelle but you still haven't told us anything about your car. To give you good advice you need to tell us a little about it, like what engine is in it. Is it still 1970 stock or has it been rebuilt, modified, replaced? Some of the questions you ask just don't have a 'one size fits all' answer.

In general you would probably need to run a higher octane gas but again, that may not be true for your particular engine. Lead additive, don't really believe it's needed. Some will say if it's a stock 70 engine you need it but there are a lot of stock engines running fine without it.

A higher octane gas will let you run more timing advance. That can help with performance, fuel mileage and it will run cooler. Do you need a higher octane? Can't answer that, don't know anything about the engine or how the timing is set now. To be safe I would say use premium so you don't risk pinging, detonation which can ruin an engine.