Just a few thoughts. Cram's Pb from training was 48.1 in summer 85 when at a career peak, and that is a direct quote from the man himself, despite some poster claiming he had 46 low ability. He also ran a 47.6 relay in late 84, which works out around 48.3 for an open run. No doubt he could probably get down to 47 high in a one off quality race on the circuit in 85 or 86.
Elliott apparently ran a 47.6 400 in training in 84. This is a quote from Wilf Paish, his coach at the time. So he was possibly marginally quicker than Cram over 400, but not as good over 1500. Although his 1500 Pb of 3:32 is perhaps not a true reflection of his ability. I would think he was capable of 3:30 in 90, whereas Cram should have been able to run 3:28 in 85.
I believe Webb's "Pb of 47.4" was a relay leg in HS. This equates to around 48.1 in an open race. In the same way that Ovett's 200 & 400 speed did not improve beyond his 21.7 and 47 mid in his late teens, and all indications from 400 relay splits between 77 - 82, suggest that if anything he lost a bit of that speed, I would doubt Webb was any better than a 48 flat guy when he ran his 1:43 high Pb. This is a time that Ovett was more than capable of at his peak.
Symmonds ran a 47 mid 400 (can't recall exact time at present, and not near a computer to check) in the lead up to London, and I'd doubt he was ever better than a 47 flat that year. It is very doubtful he will ever improve his 800 Pb as he was rabitted pretty much all the way, unless he maintains his 47 low 400 speed and improves his 1500 endurance next year.
Cruz is fascinating. He has no particularly impressive performances over 1 lap, but his official web site credits him with training PBS of 10.86, 21.73 and 46.00. The fact they are to the nearest hundredth would seem to imply they were FATimes. His best 1500 was only 3:34.63. His endurance didn't last much beyond 800. His 1000m Pb was an attempt on the WR a few weeks after his LA victory and he fell short with 2:14.09. Granted he never made another serious attempt at the event.
Kipketer had a weak 1500 Pb of 3:42, although I doubt he couldn't have run quite a bit quicker at his best in the right race. A 3:35 - 3:37 seems very plausible. Although his official 400 Pb was almost identical to Coe's with 46.85, he must have been at least as good as Cruz's 46 flat best. Indeed, a week or so before his 1st WR in 97, he ran a 45.4 relay leg for Denmark in the European Cup. That would imply about 46.1 for 400m. This has to be towards the slower end of his 400 ability at this time. I have trouble believing he couldn't have run sub 46 for an open 400 in 97.
Like Cruz, Coe has run a 21.7 for 200 in 81 and several sub 46 400 relay legs. His 45.6 in early 81 after front running a 1:44.0 ninety minutes earlier, was with a stumble ( someone else posted the link on this thread) and was worth at the very least 46 flat.
That year he also ran a solo 3:31 and a 3:47 mile. He believed that he would have run 3:28 in the former race with better pacing to 800.
I think there would have been little difference between Cruz 84, Coe 81 and Kipketer 97, over 200 or 400m as the evidence suggests. We also know that Coe was better over 1000m and significantly better over 1500m. Which makes me wonder how much faster Coe could have run 800 in 81 had he had some serious attempts at his own record.
Of course this is conjecture, but in reality nonetheless, Coe is the only man who has run a 46 and a 3:29, some 30 years ago.