318 rebuild/overhaul kit

Oh, very good choice and nice find, BTW. I really like '68 to '69 Darts. If HEI, a Mopar type electronic distributor with Trail Beast's HEI system or the like is a viable option. If sticking with the Mopar system, a used electronic box out of the junkyard from the the non lean burn set ups are better than the newer Taiwanese or Chinese stuff from the parts store. That BBD carb (just guessing, if it's from the '68) is notorious for poor accelerator pump performance. If your budget can stand it, look for a used Edelbrock performer and a 500 cfm Edelbrock carburetor, it will pay for itself in fuel mileage and street manners. With whatever manifold you use, plan on checking your manifold fitment closely to prevent vacuum leaks. Few things more frustrating than having one suck oil from the valley after getting everything put back together in a fresh build. You can use your old gaskets and and a hole punch and lead shot to trial fit everything. Punch holes in the top and bottom of the gasket flange. Put the shot in place with a dab of silicone so it doesn't fall out, torque the manifold on, take it back off and measure the shot with a dial caliper. Here is an article about what you are shooting for on clearance, I use the Hughes method but use lead tire weight compressed and drawn in a vice with a little white grease to do the same thing.
http://www.hughesengines.com/Upload/TechArticles/INTAKE_MANIFOLD_SEALINGJULY2015.pdf