HIF6/HIF44 carb inlet manifold and linkage 1275 motor

From the sounds of it, you have built a pretty good motor. I would suggest that twin 1 1/4" are a little lite for the job to say nothing about the fuss of keeping twin carbs in sync, etc. Twin 1 1/2 will result in poor bottom-end performance which is not good for a streetcar. The use of a weber is the best option BUT it is not an easy task to fit a manifold that results in any real carb benefits unless you cut into the firewall and then only with the use of a Dyno will you actually get the benefits from a weber. The bottom line for me would suggest you use a single 1 3/4 HIF carb. Good bottom end while not sacrificing top end. check this out: https://www.minimania.com/part/MMKT0400/Classic-Austin-Mini-Hif6-hif44-Carb-Inlet-Manifold-And-Linkage-1275-Motor    

If you have your heart set on a Weber set-up I would suggest:  https://www.minimania.com/part/P4-004/
This weber is far more user-friendly and can simply be bolted on with no dyno tweaking needed.

Mini Mania Tech Team

The Classic Mini Parts and Accessories Experts