No valve adjustment?

Sounds like you found a great mechanic, if the price is right, and who would try to jerk over a policeman?

As stated above, if your spark plugs go into removable tubes, you have the earlier head. Easy to see, because there is a rubber gasket around each tube that likes to leak, but a new seal set is ~$2.
If they go into solid holes in the head, you have the later head (~1978?), not all of which had hydraulic lifters (~1980?). The problem is, with that head you can't pull the lifters up thru the pushrod space, so would have to remove the head to change them. Personally, I would prefer a hydraulic setup since regularly adjusting valves is not my idea of fun. Indeed, I converted my 273 to hydraulic. You can at least pull your pushrods and insure they are the later hollow ones with holes for hydraulic lifters, and (as mentioned) your holes aren't clogged.

Thanks everyone for the great explanations of valve train oiling. I wasn't sure how Slants worked. In a related story, when I had my 69 Slant in 1994 I found one cylinder had no compression and was just passing raw gas. As a temp measure (since working away from home), I decided to disable that cylinder, aka the Cadillac 2-4-6-8 method. I just removed the lifters and pushrods. When bragging about my cleverness, a coworker who was old-school hot rod told me that would lose oil pressure with the lifters out. I went back, installed them, with the adjusters backed off and a weak spring to let them move up and down without opening the valves. Now I see that just removing the lifters was OK.