I'd stay 3 1/2" all the way through. With the bullet mufflers there is no noticeable difference in ET and though it's way quieter than open headers, it's still too loud for the street which is why we slip on a couple of supertrapps. We just replace them with turndowns at the track. If you just want a quiet (ish) 2 muffler system, pick your muffler wisely, some are better than others when it comes to flow / silencing. up
Edit: You can make em out here cool
[Linked Image]

Last edited by Tig; 11/17/19 12:08 PM.

'74 Challenger..9.46 @ 145.9 1/4, 6.001 @ 118 1/8 so far. 4023lb !!! # N/A, Marsh performance 655ci, Indy Maxx, T/R, Indy 600-13 X's, Street legal, pump gas, full interior, Cal-Tracs, mufflers, 3:73's and real 10.5 radials.
9.51 @ 142.4 1/4, 6.003 @ 114 1/8 with our old mule KB, 572-13, 580 wedge.
RHD '68 Barracuda Fastback 323ci street/strip. Best ET 13.88 @ 99.03