question on E7TE headas

I recently bought a set of rebuilt E7's from Allied Motorsports in Atlanta to replace my old e5ae heads. Looks like the work is excellent with new guides, posilock valve seals, five angle valve job and resurfaced. I am going to grind out the thermactor bumps to improve flow, but if I port match the exhaust ports, will I hurt the velocity? My stock exhaust manifolds are also plugged up with bumps on the inside of the sides to where I can,t get my finger very far in. My engine is a 86 351 HO out of a F-150 with very few miles on it.It has a Comp Cams extreme 4x4 cam with 262-270 deg. .493-.512 lift 111deg LSA.
What I'm trying to say is will I hurt the performance by porting out the ex ports and adding a set of Hooker full length headers? Also how much better is an aftermarket aluminum manifold over the stock iron one? So whaddya say?
Thanks from Bud in Arizona

the E7 heads really come alive with the exhaust side worked.

I would be careful at the port. Most improvement is made in the area under the valve and get rid of the hump. Search home port E7