my 67 flatbed wont stop

[Xeen]

If you want it to stop and stop right now you really need to convert it to front disk, you can find local guys who are selling the kit from trucks they have parted out easily enough for around $175 you will probably have to swap out the calipers for some rebuilt ones from O'reilly they are $20 apiece. If the guy has a couple of different racks to choose from try to get one with tight tie rod ends, if not you will have to buy inners and outters for it.
If available you can also pick up the GM disk brake master cylinder, prop valve, booster and linkage assembly that goes through the firewall, make sure you grab all the bracketry for it as well.
It's worth the expense because the truck will stop on a dime instead of sorta stop.