I've checked with Carol Nash, who are like hugggge...so long as they are 3 yrs old or more...doesn't make a difference...
I do believe though...If your going for a specialised insurance (such as classic etc) then they might ask and it may affect your premium...best to ask them what the difference would be without the pnts and then take that quote elsewhere LOL.
Modifications : Always a tricky one...again varys with insurers...a Big Rebore is 15% on top with most of them...other mod's vary :S