I had a coupe with Carl's 3.5L, 1.3 motronic, and 5spd conversion. It was a great driver; lots of torque and ultra smooth and reliable. I would go away on long deployments (7-8 months), come back fire it up and it would run like it did when I left; Honda like reliability. That being said, of my coupes recently underwent an auto to 5spd swap by Don Lawrence in SF and some fine tuning by Classic Coachworks in Monterey and it is running very nicely. With carbs, it is not as hassle free as running fuel injection with modern engine management but it is not that bad either and I only feel the loss of some torque compared to the 3.5 setup. You may want to make sure your engine/carbs are dialed in before you sink a lot of money into bigger engine. I would; however, recommend the 5spd swap wholeheartedly, in particular, Don's setup. He does it right and I can say honestly that this is the sweetest shifting car I have ever driven; thanks Don!
I have a coupe being worked on now that is going to be a bit more radical; 5spd, 3.5L, Megasquirt II, custom cam, S38 ITBs, IE headers, custom exhaust, and more. Once I get it back (hopefully at the end of this month), I will let everyone know how this setup feels.
-Walt