[prostreetC-10]

Good questions. There are no jets that are changeable in the rear. It's a fixed metering "plate" that has fixed jets and fixed idle bleeds. You don't jet a carb to cubic inches. You jet and power valve a carb to obtain proper air/fuel ratios throughout the rpm curve. holley jets their carbs a tad rich out of the box and at sealevel. You will probably be fine. You can mess with the jetting down the road on the primaries if you want since the carb will spend MOST of it's time in that half of the carb. It's hard to get a stock box carb to be right on throughout the curve with the factory metering blocks. You are either going to be close down low or at WOT. Not a big deal in your application. Realize though that most of those (if not all) 307s were 2 barrel motors. That 600 is about max cfm you would want to use. The Holley DVD also tells you the old school way of reading plugs for jetting.