To replace the stock exhaust to the stock header, you will need an exhaust gasket. All else is simple, although you need to remove the Remus bracket to get the stock bolt back in (at least I did).
I put 2 db reducers in the Remus and still prefer the sound of the stock, but this time I reinstalled the stock can and left the Remus header. Header is slightly shorter and doesn't fit fully into cut outs in stock muffler. I have used a shorten exhaust gasket, clamped and sealed the potential leak points, but will probably need a better solution this summer. To tell which header you have, the stock header shrinks in size from block to muffler inlet and the Remus grows in size.
My current record is 112 MPH on dash which is about 105 true (stock muffler and stock header). In addition to the better designed Remus header, I am doing a PC V, so I may be able to eek out an additional 1 MPH
Going up on the front 1t helped me not hit rev limiter in 6th.