Not sure about 68, but my 70 Sport Satellite with A/C, has the vacuum canister, bolted under the battery tray - as my car is NON power brakes, the vacuum "t" on the manifold, is just a single small nipple on it. The hose goes from there, ALL the way over to the vacuum canister, and then lots of hose from vacuum canister to the control on the firewall. . . pretty sure your car would have a vacuum canister as well . . . check the FSM . . . oh, and the vacuum canister on my car, looks exactly same as that used on the air grabber cars ! Think it is same as was used on C Bodies as well (check out cbodies in wrecking yards - usually located between fender and inner fender, so well protected)