I think you mean this kind of sound!
I love Peter's tone too, and though I'm far too young to have seen him in his pomp, he is one of my favourite players. The Matamp setup you refer to is I think a kind of amp which eventually became Orange amps. I think he used one of these on Albatross (playing a Strat, incidentally). Apparently, though, he was never that fond of these, so that by 69 ish- certainly by the time that Peter Green's Fleetwood Mac had reached its very peak and all the way through until Peter sadly crashed and burned, he had ditched the Oranges for Fender Bandmaster heads with Fender cabs. Hence he was getting some lovely clean tones but when he wound it up it really roared too.
So you'd be dead right in getting a Fender- or Fender style- spring reverb to cover that part of the sound. As for the delay element to his tone I always assumed he was just a reverb user. Listen to the track below for example and it sounds to me like he's just punching the reverb in and out via a foot switch.
Then again, you could be right about the delay. After all, a friend of mine who is older than me- and who saw Peter Green's Fleetwood Mac several times (lucky sod!!!)- swears that he always used to see a WEM copicat onstage when they played.
Don't forget also that to get the true Peter Green sound you need to get an out of phse pickup sound. I dont know about you, but a Strat in the in-between position never sounds quite right to me. I did once have an Epi SG that I modded to copy the Peter Green out of phase humbucker sound and it did work. It's quite an appealing sound I always thought.
Anyway, good luck!
By the way the solo that kicks in at 3:00 is probably my favourite by anyone ever.