Magnum Adventure

My back has been hampering my progress. I am hoping to get the old heads off this week and get the cam degreed. I will have to buy another pushrod length checker, because the one I have will most likely come up short. It will be intresting to see what the LA deck height, thin head gasket, and LA retrofit roller lifters add up to in terms of pushrod length.

How much will I be hurting this combination by running an old LA M1 dual plane intake? Does the LA M1 fit somewhere in between the Edelbrock Performer and the Performer RPM as far as performance?