I know Best Machine has used the Indy 440-3x with adapters on B1 engines. I did an FBS single dominator manifold once. Its basically a B1 manifold with the flange end altered to fit FBS heads. Cut the floor out and raised it in the plenum area and reduced the runner taper a bit. Had 121% VE on the dyno. I'm not familiar with the cubic inch of your engine. Alot depends on that and the rpm you run it to. Being a nitrous motor I don't know that the manifold is a problem.

Does your car have a race pack or other data reading and storage? If so when does the RPM rate per second start to slow down in 2nd gear?
if it isn't below 7900 RPM you may be short shifting it now.
A engine dyno using a water break is nothing like the motor has to deal with in the car, I learned a long time ago to use the dyno to get the motor close on timing ad jetting and finish the tuning in the car based off of the spark plugs and time slips.
I change the shift RPM by 300 RPM last year in my S/P car from 7000 RPM up to 7300 RPM, the car ran 8.886 at 148.3 MPH having it shift at 7000 RPM, Powerglide 5300 stall nine inch converter with a Biondo 400 box and Biondo air shifter, moving the shift RPM up to 7300 RPM made my car run 8.886 at 150.6 MPH 45 minutes later
I would try shifting yours higher in 200 to 500 RPM increments to find the best shift RPM with your combination

OK, other threads and my engine has me thinking, what options are out there for B1 intakes? Im told mine is holding my combination back. The runners are too long with the spacers, so whats the option? Im thinking cut it down the middle, bolt it to the heads and fill in the plenum? Has anyone modified a B1 intake? Also why is it SO thick and heavy? LOL
I have seen Indy intakes modified to fit on a B1 , any one do that? and did it help compared to the B1 intake?
Just looking to see what others have done, im not the normal bracket racer, and my combination is tailored to a lot of nitrous or whatever it takes to make 1500+ ?

I don't know what equipment you have access to Tony, but you could cut the intake in half and weld flanges on so it bolts together in the centre. There is a bunch of material in the plenum of those intakes, you could get some material out of there, while you are there (if you haven't already).

Those castings could certainly go on a diet, someone should do a lightening program for them, not that many people would use it.

Tony are you still using the stock cam core size?

Titanium valves would also be a good addition but Id bet you already have them, at least on the intake side. If you are spraying a lot might be other/better options on the exhast side. A B1 intake valve is like the intake, big and heavy and most are replaced with titanium early on.

Couple questions. Stainless or Ti intakes? Is the rpm limit in the car on HP, while spraying it or both? I agree that a larger cam core would help. The 557 B1 I had would not pull past about 7600 till I put Ti intakes in it. That was HP only.

When I bought Steffs Challenger and was running it NA, we had the same issues you are having. I had several conversations with some in the know guys and the general consensus was that the stock cam core was inducing a ton of valve train instability. With the weight of the pushrods 9/16 and the valve and the spring pressure needed with 7500=8000 RPM the cam was twisting I did verify after 20 runs 8200 rpm trap the cam was a pretzel. The single biggest upgrade according to Bishoff and Alan Johnson was to step up to a 55mm cam core. They both told me the B1 intake was not the thing holding the combo back. I never got a chance to put the 55mm cam in I bought it and just gave up on the program. Thought I would pass this info along.