Hello, Can anybody help?

I'm thinking about buying a 1983 campervan with a wasserbox engine.  
This engine has done 119K miles, but the heads have been overhauled 
some time in the recent past. (no receipts, but claim seems quite 
geniuine).  I would like to buy this van for a 6000 mile trip, but I 
have too concerns:

1) There seems to be quite a lot of tappet noise when the engine starts, 
however this dies away when the engine is warm.  But when cold, this is a 
real mechanical rattle.

2) I have carried out a compression test and get the following results.  
The two back opposing cylinders read around 150psi, yet the two farward 
opposing cylinders read around 110-120psi.  This test was carried out 
with the engine warm, all spark plugs removed.

I'd like to know whether these two concerns are serious, whether they 
indicate impending mechanical failure, and the concequences of the 
failure. 

Other observations, well I've driven the van and it seems fine.  The 
antifreeze is clean, no crud at all.  I've looked at the heads from the 
outside and I can't see any seepage.  There are a frew oil leaks on the 
engine in general, nothing appears serious.  The pluges are clean after a 
run, and there is no smoke from the exhaust.

I'd appreciate any advice on this beast.

Tim