Do I need to change the spring and weights out from the dist. after the 305 to 355 swap. This is in my 79 Camaro with an automatic tb350.

 

I would reuse the old distributor, if it worked good before.

 

But how do I know if this new motor is getting all the total ignition timing it needs to run at its best?

 

A timing light should give you that answer, if you install a timing tape on the balancer. Just fire it up, and see where the timing is at idle, and at various rpm's as you watch it with the light on the tape. I would hope total timing would be around 34-36 degrees, and not go any higher. If it goes higher, then you may have too much initial idle timing, or a problem with the distributor or vacuum advance.

 

Thanks for the info, I will have to grab a timing tape and wrap around the balancer like you mentioned. I'm tossing the old original worn out dizzy and picking up the MSD street fire on friday. Plug and play unit, the original had to much play in the shaft and the bushings and pins were worn also. Time for a new one.

 

Are you getting the Street Fire distributor, or Street Fire box? If you're getting the Street Fire box, I'd highly recommend not getting that model! The Street Fire box is a potted box, so it's poured full of epoxy, and can't be repaired should it ever have an issue.