The REAL skill was in the negotiating. Unlike "pinks", there was no yelling, figet-pointing or name calling. It was more like playing Poker. You talked money, location MAYBE owned up to about 5-10% of what you really had & what the car could do & run 'em. Hopefully no data would leak out & you could win. That goes on today I know in every type of racing (just TRY to get specs on a S/S racer's set-up for example) but the serious street-rats had it down to a science which back then was rare.
Of course if you were unlucky your opponent would have access to some guys who actually worked at gathering intel on your opponent & would have car specs, perhaps pictures of your opponent that could tell you just how fast he really was or what latest modifiction he made . He may help you or you'd bribe him for the info and get an edge on negotiating the race. That stuff hasn't changed but I'm sure modern streetracers are even more secretive.