It's a fair buy for 8k for two rare bikes. The red bike looks pretty clean and ready to go. The downside is that they're '71/72 models with the earlier 'grey ghost' style engine. The later ''73/74 model had the VR 'crinkle cut' engine. My learned Montesa compadres would be able to tell you more about the mechanical differences between the engines (Jared?) The Rickman frames are essentially the same between all Monty models, the only major differences being side panels and pipe.
Folklore has the Rickman Montesa as coming in substantially lighter than a VR but I seriously doubt that. The Rickman is still pretty light though and on top of the great Rickman quality framework you get the best brakes and hubs in the class, almost as good as Yamahas little conical jobby. I'd race the red one as is and do a concourse resto on the other if I was going for them.