1977 Cylinder Heads

Hello. I been working on my first engine project 1984 460 ford in my Tow Rig F250 xtra cab pickup. I bought another engine it is a 1977 from a factory propane camper special, it even came with the factory pump block of plates and only propane induction , it also only had 68000 miles on it when I got it. Now what I wondered was now that I have this 1977 engine all apart i was going to get the Heads hot tanked and pressure tested, if it passed this then new valve seals and back on to my 1984 f250 460 thats still in my truck, The big question is I wanted to increase the compression since I run dual fuel (propane and gas) how much could be removed from these heads with out incurring pinging on low grade pump gas (87 octane) Thanx Mike

D3 pretty sure dark outside right now and theyre in the trunk of car, Are numbers on head? ALSO would a 1977 factory propane engine come with hardened valve seats from Factory? Was that ever even done? Around here (kitchener waterloo0 you take youre chances on getting ANYTHING MACHINED RIGHT FROM ANY SHOP its pathetic, So if I need valve seats ect done who would yo urecomend ? Thanx Guys Mike