Well I paid £100 for my 1275 Midget engine with known smokey valve guides but I was unable to hear it running but its turned out to be a reasonable engine but a bit rattly so I will rebuild it in the winter.
If you cant hear the engine running with luck it should keep the price down, but do you know what size it is as the 1275 is worth more than the 1098, the propshaft is no good to you but the diff might be if its a 3.9 as this will lower crusing revs but will lower performance.
engine thats been raced and not used for three years
Now the big question is how much has it been raced, but if the price is reasonable and you are prepared for a rebuild you might be lucky.
Let us know what the owner says about condition,size & price and we should be able to advise futher.