I asked a similar question and this is what vvega wrote:
ok here we go
all bluetops are the same :
small cranks,3 rib block,bigport and tvis
red tops there 2 different versions
the tvis redtop and the non tvis redtop
the tvis redtop is basically a redtop bottom end with no squirters
the pistons are also a little different been lower compression
the head is a bluetop basically with a red color
they also use a 3 wire dizzy
the you have the real redtop
100kw
smallport
oil squirters
no tvis
4wire dizzy = true crank angle sensor
higher compression
there are more changes than i have noted but ive tried to keep it fairly basic in understanding
v