I just finished up working on my instructor's '97 F-350. It needed a new oil pan & dipstick tube. When I got the oil pan, I measured all dimensions to make 100% sure it was the same size as the one that came out & it checked out OK. I also made sure the new dipstick tube was the same length & besides a really bad bend in the old one, they're both the same length. Now, when I put the oil in it today, I primed the oil filter & installed it. Then I put in
3gal of oil & the dipstick's reading almost to the full line in the operating range grid......
I haven't gotten to start the truck yet to build up oil press & let it warm up(because of rain), but whatever little the filter would need to fully prime & whatever amount of oil will fill the engine I know won't require another gallon. My NBS takes about 4gal. Do OBSs have less oil capacity than an NBS????