Danny, This is a common problem in cars too. Your vehicle has the standard heater & the only repl. cores made are the deluxe models. NO problem....Where the cable operated water valve would normally go in the box, leave it out. One less future in-cab leak. With that extra space in the box, you can solve your wrong-position plumbing problem. Get some 1/2" copper fittings & a stick of hard Type L tube at your plumbing supply & make up a manifold adaptor to get it where you want it & thru the firewall. The tube O.D. will be 5/8", just right for your hoses. Run a bead of solder near the tube end to guarantee the hose & clamp can't slide off. Get a inner-fender mount type of shut-off valve, when that starts leaking someday, you'll be happy it's not inside the heater box. If you wish, you can also at this time upgrade from the single-speed to a three sp. blower. Get about any resister off one that mounts inside the heater box/duct outlet & put it in yours. Get a three sp. blower motor & squirrel cage that'll fit in your box, many are similar. Repl. your existing on/off switch with a three-pos. one. Doug
