Any headers you install will require the 90* oil filter adapter to be removed first. The TTI's will work well with your current engine as well as the larger engine. They step from 1 5/8" to 1 3/4". The dyno comparison shows they work well on mild engines.
Mopar Muscle exhaust dyno comparison:
http://moparmusclemagazine.com/techarticles/155_0307_exhaust/
I have them on my race car and have run as fast as mid-11's at over 3,530 lbs! Several other fast 360 Mopars in IHRA have them too! If you have the exhaust system routed to match the headers you have now, it will likely require some more modifications to line it up with the TTI's!
Just a suggestion, but it seems you could save money in the long run, which will help pay for the TTI's, if you get them installed first!
* If you have the time, you can probably install them yourself. ($300)
* Sell the 90* oil filter adapter.
* Sell the Summit headers.
* The rest of the exhaust system will be
done the first time. No re-aligning the pipes for different headers.
I would recommend the ceramic coating outside as well as inside.