It is true that most people did remove them, but if you are going to run reflectors on a classic bike I would definitely want to use period correct versions vs. something more modern.

Reflectors on bicycles sold in the USA changed quite a bit from year to year during the '70s, mainly due to increasing CPSC requirements at the time. If you want to be period correct the most popular (and best looking IMHO) type of wheel reflectors used by many if not most mfrs. in 1974 was the Cateye RR-220, which was available in both black and white plastic versions. There are several available on eBay, including a NOS black set including a front reflector and a NOS white set including front and rear reflectors on eBay.

The front (white) and rear (red) facing reflectors generally used up until '74 were round 2-1/4" flat types made by Gulco, Cateye, Sate-lite, Stimsonite and others. Starting around '75 the reflector requirements changed to require wide-angle reflectors that were larger and thicker (and uglier) than the previous ones, and the front and rear came in shapes other than round.