The backfiring could be a burned valve or bad timing. The surging could be bad timing or carb issues. Or it could be that everything is wrong. Start with a valve adjustment on a dead cold engine. Then do a compression test. If the compression is good in all cylinders (120-150 PSI or so). Install new plugs properly gapped then set the dwell (new points) and timing. Check for vacuum leaks - easiest way is to spray carb cleaner on all vacuum connections when the car is running and if RPMs change there is a leak. When you set the timing make sure that the distributor is advancing properly by checking the timing at the different RPMs specified in the book. Also, the fuel enrichment valves on the carbs can easily be in the wrong position if the linkage to them has been removed at some point, so if they don't seem to work properly investigate this. Next remove the linkage from the carbs - the rod from the accelerator linkage and the rod connecting the carbs - and set the throttle plates on a warm engine so the idle is about 800 RPMs (standard transmission). If you don't have a Unisyn you can use a piece of tubing and listen to the suction in the carbs. They should sound about the same. Then adjust the idle screw to attain the highest idle. If the valve adjustment, timing/dwell and vacuum are not right you'll never get the carbs right. You might also check the manifolds and carb bolts for tightness. Good luck.