Screwed up: mixed oil question

[72gord]

Went to pick up the 68 1 ton at the local sawmill (slab wood hauler) and it needed a quart of oil, in a yank I grabbed a quart out of the cab and dumped it in (keep engine oil and atf for the dump bed in the cab) after I finished I noticed I put in atf So now I'm wondering if this is going to cause any engine damage? The truck is 4 miles from home and it is around 0 degrees so I don't want to change it there if I don't have to. This is a very tired engine, runs great, but uses quite a bit of oil....just don't want to have it lock up or flatten a cam lobe by my screw up. Any input would be appreciated...thanks in advance