The AX-15 will bolt directly up to the 304. But you will need new body mounts and the 304 stock doesn't put out that much! I am pretty sure stock its only 130hp.
The AX-15 can put up with a stock 304/350/360. Once you start beefing the engines up that is where you start running into problems. It also depends on your driving style, if your trying to drag race at every stop light or smashing the pedel you should be fine.