Check the engine and transmission supports they could be bad. Apply the emergency brake raise the hood put it in second or third gear. engage the clutch slowly be extra careful if the motor rises you should know.
A chevy 327 is one of the best. If you do the work yourself change the cam and lifters, and the intake along with your exhaust you will see a vast difference. If the carb is good you can leave it a carter or rodchester are good street carb
