Heater Hose Locations?

[81GMCSierra1500]

Hey again,

My truck's heater hasn't been hooked up since I bought it, and I'm slowly tackling all these little issues before the full restoration begins next spring, and I'm just trying to hook up my heater, to see if there was any particular reason why it was unhooked... Where do the heater hoses run... i.e: the hose from intake manifold goes where, and the hose from the pump goes where (upper/lower port). Once that's done, I need to find out why I have water leaking from the top of the heater core housing (interior) into the cab and onto the floor. It;s not a major issue, it's more annoying than anything else, but does anybody have any thoughts on that? I'm wondering if it's a cowl seal or something, caused by rainwater leaking into the cowl, and through into the cab... Thoughts would be greatly appreciated, surely somebody out there has had this issue before...

Cheers guys,

'81