I spotted the 801s in classifieds and wondered if the HD8 lenses can be put on my 808s for improved picture also the tubes are only 2years old would they match and to finish any circuit boards compatible?
Optically the lenses will be the same though the mechanical design of the later 808 will be better. So unless there is something wrong with your lenses then I don't see any advantage there.
Many boards on the 801 and 808 series were similar so there are usefull bits to be had but the support will tend to be the otherway ie some 808 boards can go into an 801. As a rule unless the 76***** number is exactly the same then don't swap.