Installing a 4bbl on a 273 advice

I shouild have mentioned that the car has dual exhausts from the heads back, and I suspect it may have 3.23 gr as the car has a 7 1/4 SureGrip and launches better than I would think with a normal 2.74.

I'll be happy if there's a marginal performance increase as I'm still planning on doing the Isky E4 cam in the Spring. I just didn't want it to run worse than the 2bbl in the interim.

Thanks again!