Rick, In the end, the value of the engine is what it's worth to you the buyer.
Just IMHO, but I would do some more investigating to see if you can confirm the lack of a serial number and I would look to see what the head casting number is. The serial# can best define what the engine may have been in originally and it would help to know which head is there as some are preferred more than others performance wise.
Roaming the web looking at engines for sale, I have seen asking prices from around $200-250 on the low end to upwards of $1000 for engines that have no proof of their internal condition. If it was me, I would want to do some more inspecting/checking (pull the valve cover at least) to look for signs of severe neglect or good care taken. With more indications that it seems well taken care of, perhaps somewhere in the $400-500 range would be as much as I would spend myself. I personally snagged a running 1962 235 for just $250 several years ago. Use your best judgement and the size of your budget to help you decide.
