I don't know a lot but maybe this helps. If you want a new balancer go to the balancer guy online. He's in Redding Caif. For about $60 bucks you will get the correct balncer for yor engine. Off the top of my head I would say that you need a 6 and 3/4 inch balancer with a 2 o'clock TDC. 305 cid uses 12 o'clock. Take of the left valve cover and make sure that both valves are closed on number 1 cylinder. this is TDC for your motor. This isn the easiest way to get "true" tdc. Disconnect your distrubutor, set the timing light to 36 degrees advance, set mark to zero and you should be good. Use a timing tab that bolt onto tha upper side of the timing cover. Be sure to look at two different ones because one is for the 8 inch balancer (used on 4x4 trucks), you need the one that puts the zero on the scale at approx. 2 o' clock.