The tyre thing is one of those old stories which you have to make your own decision. Museum cars are fine as they generally just sit on them. The issue is the age hardening of the older rubber technology compounds (IIRC). These would glass over and become so hard there was no flex or grip. An infamous bus crash in Cornwall was attributed to 35 year old tyres with loads of tread but no grip. However, modern-er compounds may behave differently. An MOT would advise on aged tyres. They can definitely be kept as show tyres to keep originality etc. or for a rolling chassis. As said most wouldn't drive on them. Excellent effort on your project. Brave man.