I have a 1970 F250 with a 360 and a C6 tranny. wondering the best way to connect the kick down linkage. what position should the passing gear lever be in? should the throttle be fully open?

having problem starting my truck. i recently put knew (rebuilt) heads on the engine, and a 1970 motorcraft carb off a mustang - i needed a two barrel. anyway. when i turn the key it takes a long time for it to finally turn over. i've tried giving it a couple of pumps of gas, and not giving it...