Just last night I was working on my engine and I noticed something I hadn't noticed before. On the block, right hand side, directly underneath the oil sender hole and just above the oil pan - a cast manufacture date. All three of the B20 blocks I have about (the original engine in the 1800E, a 'spare' B20 block I have, and the PV's block) all had a date there. Although all three blocks are from a fairly short time span of late 1970 to mid 1971 - I don't know how long they put those there.

The heads may have been changed and/or modified. You really have to measure the thickness to get an idea of what it is. In general terms:

- Umbrella valve stem seals - peaking through the oil cap see if there is a rubber disc on top of the valve spring retainer. If so - B18 head with little intake valves.
- No umbrella seals - no injector ports - a B20B head - medium intake valves.
- Injector ports - either a B20E or B20F head. One way to tell the difference is to look for a machined ithsmus leading from the center headbolt on the manifold side to one or both of the adjoining injector perches. No 'ithsmus' - it most likely is a B20E. If they exists - it is most likely a B20F. Although it is quite easy to have a B20F head shaved down to make it higher compression like the B20E - best to measure the thickness before you make assumptions about the compression ratio.
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I'm JohnMc, and I approved this message.