The only other advantage I know of from running longer connecting rods is a better crank/rod ratio. As far as your question about the lift I would stick with the lower of the two. The 305 AFR only had one cfm difference between .600-.700 in stock form, therefore the lower lift should extend valve train life. It is only a guide line but I have plugged in the figures for a few build ups I read and the one with best power fell within the 7.5-8.5, usually ~8.