Here's a thread that might help with the linkage question.
http://67-72chevytrucks.com/vboard/s...=shift+linkage
Remember you need about 3/4 ths of an inch of yoke sticking out of the end of the tranny for movement. the forward holes are where most v-8s are mounted to give firewall clearance for the HEI distributor. The crossmember is different for a standard and an automatic IIRC. Probably the best bet is like JIM says and bolt everything up and then get the driveshaft lengthened.
When you post you need to give more details on your truck. Engine, Trans,etc. BTW thanks for your service.