There was a set of 1.875 TTI headers for sale here on FABO.
I have tested step headers, merge collectors and step headers with merge collectors until I was sick of it, and neither the step or the merge collectors did squat.
You didn’t mention the LSA...I hope it’s not more than 109. Even with those heads, 109 is about as wide as it should be before you start giving up ET in the gear changes.
IMO, if you are going to do a step header, or use merge collectors or use a 4-2-1 header, you have to develop and make everything work with those styles of headers and collectors. I know the 4-2-1 headers use a very small primary tube and that design with a merge collectors will seriously over scavenge the chambers. So you need to know that and make the cam timing for that system. I think a 1.875 primary with a 3.5 inch collector is a must. A 3 inch collector is way too small for use with mufflers.
Also, keep in mind almost every header has a collector that is too small and way too short. If you are running full exhaust, it should be collector diameter all the way back. If you aren’t running full exhaust the collector should be about 18-24 inches long as a start and test from there.
That’s what I’d do. Also, if by some stretch of luck, you can find a set of Hooker 5303 headers i would buy those. It’s what I run, on 340 inches. They are like hens teeth, but I’ve used enough of them that I know they work. I’ll also be on the dyno hopefully by June, and I’ll test the 1.875 headers against a set of 1.750 headers I have access to, just to show that big headers dont kill torque.
