I have a 68 Barracuda M/T with TTIs and NO scattershield. It looks like I could put one in there and still take the headers down as necessary. But as Rumble says....it might be tuff. However, uncoated TTIs last for at least 5 summers and 4 winters, before rust perforates at the merge on the driver side where the salty snow/water collects, and another year or two before the other side needs work.And the gaskets, at least mine have survived 16 years and multiple engine-swaps. (I used to run a teener in the winter).
So my question is, why do you wish to pull them off,from time to time?