For Cash: his arrest at the Mexican border was for importation of Dexedrine capsules (so probably Spansules, i.e. d-amphetamine 15mg CR) and Equanil tablets (meprobamate, probably 400mg).
For Jerry Lee Lewis: retrospectively, he said his favorite was Desbutal (d-methamphetamine + pentobarbital [aka Nembutal]; for the IR version, it was 5mg meth and 30mg pentobarb, while for the CR "Gradumets," it was either 10 or 15mg meth and 60 or 90mg pentobarb, respectively).
I don't know specficially for Waylon Jennings (other than the fact that cocaine seemed to replace them for him by the mid-70s), but in general, Dexedrine was one of the widest prescribed as 5mg IR tablets or 15mg Spansules, as was Dexamyl (d-amp + amobarb, similar to Desbutal), also in IR and Spansule formats, and similar ones like Eskatrol (which combined d-amp with prochlorperazine, a sedating antispsychotic).
These were also the ones that lasted the longest into the 70s and 80s, in terms of actually being prescribed, along with Biphetamine capsules (a 12hr CR 50:50 combo of amphetamine and d-amphetamine in 7.5/12.5/20mg -- essentially Adderall XR with a longer duration due to the propietary CR mechanism), which were known as "Black Beauties."
Black Beauties were one of the more common forms of pharmaceutical speed sold by pill dealers on the street in NYC at least into the early 80s, though some were probably counterfeit or bunk at the point (like Ludes). Legally manufactured "lookalike" Black Beauties (sold in the back of High Times etc.) containing high doses of PPA+ephedrine+caffeine became a problem in the 80s, when a number of people had strokes from popping a few of them, when that amount of amphetamine would've been in authentic Black Beauties would've been basically harmless.
While pharmaceutical Benzedrine ("bennies," i.e. racemic amphetamine in 10mg tablets) may have been around in the earlier days (say, the Hank Williams era), it was largely displaced by Dexedrine from what I can gather, but illicitly-diverted or-produced "White Crosses" (containing racemic amphetamine, hopefully, rather than ephedrine/PPA/caffeine) were one of the earlier forms of black-market speed.
Pharmaceutical methamphetamine was also prescribed during the 50s-60s, with the injectable Methedrine ampoules (used most notably/notoriously by Lenny Bruce) being the first to be restricted starting in the early 60s, but Desoxyn (tablets and Gradumets) and the combination drugs remained relativey common throughout the 1960s. However, they were increasingly stigmatized and the hardcore "A-heads" of the late 60s mostly used black-market crystal methamphetamine that was made in illicit labs, setting the standard for later generations after Rx methamphetamine dwindled during the 70s. Obetrol was reformulated from a 50% d-meth, 50% racemic amphetamine combination, to a 50% d-amp, 50% racemic combination in the early 70s; in the new formulation (sold as 10mg and 20mg IR tablets), you have the precise formula of today's Adderall, which is what Obetrol was rebranded in the mid-90s after being purchased by a different company and approved for ADHD.
Elvis was prescribed Preludin (phenmetrazine) among other things, which was very popular in Sweden in the 60s (and which the Beatles took during their residencies in Hamburg during the early 60s) and as an IV drug in some parts of the US. Other diet pills like Bontril (phendimetrazine) and Tenuate (diethylpropion) stuck around longer into the 70s/80s. Ritalin was also present throughout the period, and was also favored by injectors, and more common in the Black community than other types of speed.
Seeing as how it's so hypersexual.
