Car runs great when cruising but breaks down under torque??

is this fuel injected or does it have SUs? Been so long, I forgot- I'm guessin' SUs cause if it is Lucas fuel injection, you really got a problem- first suggestion is to find a really good classic car mechanic like my friend Steve here in Santa Fe- really, he has his own shop and only works on them one at a time- a beautiful car like yours needs special attention to keep it running right- not the "assembly line" procedure of ordinary garages, as good as they may be- I think the judge is right though, it's probably fuel- specific suggestions: check the fuel filter, fuel lines, gas tank for dirt and rust- do you know if the gas tank is clean, or new replacement? Man, a 100 year old gas tank is no good and it is where you should start- also, replace those SUs with Webers- get somebody good to do it, like I said

I found the problem to be in the gas. The car sat for a couple years so I think I picked up something in the tank. I added Seefoam to a full tank and it cleared up.