There are two measurements of compression:

Static compression is a calculated number regarding cylinder sweep, piston surface volume, how deep the piston is in the cylinder, gasket thickness and combustion chamber size. Flat top pistons make this easier but some even calculate right down to the small gap between the first ring and the cylinder wall.

Dynamic compression factors valve timing as well.

One of the reasons a "Race Engine" gets higher compression is to compensate for longer cam duration and/or overlap.  There are calculators on line that will tell you both types but you do need to know the cam timing, bore and stroke numbers and combustion chamber size.  This will be helpful as there are general guidelines and if your combination is way outside the numbers there is cause for concern.  Otherwise if it works - use it. You may have to increase octane of lower the ignition timing.

Building an engine is a "system" intended to have appropriately matched parts for the purpose.  Sometimes you get fortunate straying (slightly) outside the norm and other times you get undesirable results. If your other engine had a different (performance) cam it may account for the lower compression readings. But not knowing the combustion chamber size differences before and after any milling of either head is an unknown.

 LOL, an original post a year and two days ago. No report back on how the "race in two months" went.

I wonder how "self retarding" the set up is given the large head cut. Something has to compensate for the slack in the timing belt.

one of the resons I am useing the roller , but you can change the rocker arms from the last year lima , its a diffrent ratio but brings in a tad of lift and a few more degres of duration and I am going to pull in a much advance as I can for lowi end torque , the max RPM will never see over 2700 , it will be swinging a 74 inch wooden propellor , yep it going on a airplane ,

The cam and rocker set up I got from a write up on Routh 66 hot rod high , has a listing for what year cam and rockers , and what changed when you swap parts , Got both of them and also going to check to see if the industral 2.5 cam is any diffrent , ( got one of those also ) as for why the lima engine in a airplane is because they are very reliable and there is one airplane that will work with it , only is was built back in 1928 with the ford model A engine , yep only forty HP on a good day but it worked , not fast but it did work well , many engines were put in that aircraft but I wanted to keep it all ford , (model A engines are getting hard to find ) but I will be useing the 2.5 with the duel plug head so I will have a secondary ign like real aircraft , the ford industral book list the LRG425 at 65 HP @ 2700 rpm so power is enough and the weight of the engine is about the same as the model A engine , just need the low end grunt to swing the prop , as for how lnog it will last , it will out live me , I work at the airport and most of the tugs here have that engine in them , I look on the hour metter (HOBBS) they have over 6 to 7K on them , they overhaul the piston engines in aircraft at 2K some go more but not often ,

What ! I thought everything on the internet was true    , but good thing I did not go out and buy thinking they would work , have to double check that mith myself , but still do not know if the industral cam is any better , the head casting is diffrent also , it was made as a duel plug head but the extra hole for the spark plugs are not machined out at all , and has the small valves and valve seats , this one had a propane carb on it , thanks for the info , guess typos always waste time and money when they look to be legit , at least I can run the engine on a test fixture with the prop and swap out the cams to give me max rpm static and find out which one is the best ,

According to the link below, the exhaust manifold looks like a turbo manifold, see pages 27, 28, & 64. 
http://www.rothfam.com/svo/reference/ford%20industrial.pdf

yes it does have the turbo exhaust manifold , first thing I noticed when I got the engine , guess this was the best way to go to run the exhaust up or down , the muffler is on top and came out of a lift that had a accident ,