Sounds like heat soak. For what it's worth, I'd take a carter over a holley any day of the week, but that's a matter of opinion.

What you describe sounds like heat soak. This can be really bad on a slant six because the exhaust manifold is physically bolted to the intake. so when you shut down, obviously the intake gets scalding, and so does the carb. my '81 was a factory one bbl, and it had a nice heat shield that went between the carb and covered quite a bit of the intake, and hence blocked heat from the exhaust manifold. You might want to look for something like that. From another point of view, my car had horrendous starting issues, but we traced it back to a vapor recovery issue and a problem with the fuel tank rollover valve.

Also, I highly suggest wrapping the fuel line to keep excessive heat out of that.

Last, that's a lot of car for a 225, it's never going to get out of its own way. Now, you could do something fun, like make a carb box and put a turbo on... boosted stock 225s can make torque that rival diesels (still don't get a lot of HP though with stock cam and head). but with 400 ft lbs, you'll still move out.

To me, the 225 had great low range torque, like right off idle. but absolutely no throttle response. So, while they do fine around town, or passing someone on the highway without having to kick down, the torque is all you have. if you push the pedal to the floor, it really has nothing more to give. that's just a function of the (relatively) small cubes, the gearing, the weight, and so on.

If you want it to sound faster, flip the lid.