Hi,
I have a TR-4a manifold / H6 carbs on my TR3a. I did that because I have the late 4A cylinder head, with the small ports. I wanted the correct, small port intake manifold so I do not have a forward facing step in the intake port.
K+N makes a tapered filter that I offset upwards to get more fender clearance. I replaced the throttle linkage with a cable. The angles were causing it to bind. The choke linkage, were the cable attached to the fwd carb hits the inner fender well. To be fair, the Inner Fender well was replaced on my car, that might be the cause of the rub.
Good luck, I changed mine about 15 years ago.
Roy G