Stock 1969 350/300 engine with headers, 2.5 exhaust, 3.42 gears, summit 1103 (.442 ex .465 int), pertronix 2 and flame thrower

Carb will be Speed demon 650 elec choke and vac sec.

Would a RPM, EPS or Air gap work well with this combo?

I would go with the EPS imho.

Is your speed demon carb a spreadbore (625) or squarebore ?

I would think the performer or performer rpm would be best. The RPM would be better if you plan on upgrading the engine in the future.

I don't have the carb yet but planning on square bore. I was thinking performer rpm too. With talk about eps unit I was wondering about that too.

Performer RPM gets my vote.

Performer probably OK as it sits. With a bigger/better cam, Performer RPM.

I plan to do a cam but it might be a while.

What are the effects of doing the RPM with my current cam? Will it still run ok?

You will be fine. If I remember correctly the Performer RPM advertises 1500 to 6500 RPMs, the Performer advertises idle to 5500 RPMs. With a cam change in the future, the RPM is the way to go. IMHO even if you didn't change cams I would still go for the Performer RPM. Keep in mind advertised #'s do not always represent real world results.

Thanks. The 1103 sounds ok and if I change it down the road it will be for a roller set up. For now I'm content with the 1103. So it's good to know the rpm will work with the current cam.

Here is some interesting manifold comparisons.
http://www.hotrod.com/how-to/engine/...d-comparisons/

The RPM did pretty well I guess, especially for the cost. I went ahead and bought the performer rpm and demon 650 so I hope it's a good combo for what I have.