I haven't played enough original bursts to say for sure. Of the Historics the R4, R6, R7, & R8 models have either identical necks or very close; the R9 neck is slightly thinner. Compared to a nocaster RI neck, an R8 is a bit thinner at the 1st fret, but tapers to be pretty similar around the 12th. IME the nocaster neck has very little taper if any. In terms of backshape an R8 neck has less shoulder than a nocaster, being a C or D shape instead of the nocaster's U.
Definitely not. The neck on the R4, R6, R7, & R8 is noticeably larger than the standard R9 ('59 reissue) neck. I generally like my necks pretty big, but the R8 neck and the one on my Fatneck 335 are pushing it a bit. The R9 neck is just about pefect; thick but not over the top like a R8 or nocaster.