Has the fuel filter ever been replaced?
Is it the stock carb? 4 barrel or 2 barrel carb?
If it is a 4 barrel carb, pull the air cleaner and carefully, pull the throttle to wide open for a second, does the secondary butterfly open right away?
If it does, then that is working properly, if it doesn't, then it may be a problem.
And with the engine warmed up, is the primary butterfly (choke plate) opening all the way?
If it isn't, then it is likely the problem and the choke needs repair or adjustment.
First thing I would do is replace the fuel filter.
Second, check for vacuum leaks. You will probably find that there is a vacuum leak around the carberator.
How well do the brakes seem to be working? There is a valve on the vacuum hose to the brake vacuum booster. Sometimes, the chack valve goes bad and can cause those types of symptoms.