318 with n.o.s. ???

Keep the MP Orange box in the car but disconnected as a back up ignition should the MSD fail. No sense in making extra work on removing it. (That's what I do) Use the MSD (Or equal) box to pull timing out for a safe running engine.

Also, do not exceed 9.5-1 ratio for pump gas with that combo. 9.0-1 would be great.
If you can find 340/360 heads, mill them down and bowl port them. 2.02 valve a plus.
That'll give ya a kick in the pants!