NASCAR Racing: Body evolution, chevy block, slow evolution

Question
Years ago teams would buy a car, remove the interior, through in a roll cage, and go racing. When and why did NASCAR switch from "factory" built cars (1960s) to the "look-a-like" cars of today?

Answer
There wasn't one specific year, it started as a slow evolution over a few years starting in the mid and late '80s. NASCAR got it in their heads that all teams needed to be equal, due to the teams whining: that this car had better aerodynamics this season, that car had better downforce the next season, we need a bigger spoiler, we need more nose, we need less ground clearance...etc. Unfortunately NASCAR went along with it rather than what they did in the '60s...fix it in your next years model. The other big factor was the switch to front wheel drive and a shorter wheelbase by the manufacturers. That just didn't work for NASCAR racing so they had to get away from buying a model off the floor and turning it into a race car.

All this added up to what us old timers hate, a car that is no more a Ford or Chevy than an Indy car is a Chevy because it has a Chevy block. It also brought around the need for restrictor plates because if those cars had all the aero packages taken away and made to look like the model you and I buy, they wouldn't be going fast enough to fly.