I thought HGH was pretty big in the USA in the 80's, and that's why Aouita would visit there for a few weeks every year. He was still boasting about its powers to his athletes when he landed a coaching job in Australia and it cost him his job.
As far as Coe is concerned, on the one hand blood doping was legal in the early 80's, so he wouldn't be technically cheating even if he did, however he was at the forefront of the campaign to make it illegal and in fact was still running 1:43 AFTER it had been officially made a PED and when he was way past his best.
I still think it would be unlikely Coe would have the brass to go for the head job if he had even engaged in anything as shady as 'legally' blood doping in the 80's. I would also imagine that Russia and their state sponsored hackers would have found something on him by now if there was anything.
The only suspicious thing about Coe is he ran really fast, so that's not any real suspicion unless you want to accuse every great of being a cheat. He ran at a time when most of his rivals (until Aouita) were from other European and American/Anglo nations rather than corruption rife African ones. He did train in Italy sometimes, where we know there was a blood doping cuture, but I believe he went winter training there. As far as I know, you wouldn't blood dope in winter.