My word they are worth messing with. Both wonderful old engines from the '40s and or '50s.
Does the MK2 have a slot on the head to vary the compression ratio? If yes, it is in fact a MK2. Metal tanks as original are available. Is it only the tank missing or the whole carby unit that screws into the rear? Pics would help a lot.
Put them into a WARM oven to melt the old castor oil, DO NOT try to turn them over as they are as you may damage them......i.e. break the con. rod. When warm oil them and gently turn them over. Clean them up with a soaking in acetone for a week and a good scrub with a tooth brush.
Value? What someone is happy to pay...........But not a fortune.