I guess he already knows, but I try though :
- JJcale
- Richard Thompson
- if he likes the Rolling stones, especilaly the Taylor era (69-74) I recommend his solos album, a masterpiece IMHO : Mick Taylor 1979
- John Mayer is indeed abit like between EC and Mark
- Ry Cooder (mainly 70's stuff)
- if he likes Springsteen I would recommend Pete Seger, J Geils band, maybe Lynyrd Skynyrd
- if he likes beatles and stones, I would add The Who and the Kinks to complete the "cream" of 60s british rock
- I guess you meant the ravellin' wilburys. So I thinks he would love Harrison solo albums, as awell as Jeef Lynne, Tom Petty and heartbreakers....
- ih he likes the hollies, I would try CSN, Neil young, buffalo springfield, the Byrds
there are of course many live abums with all these well known musicians together, legendary concerts :
- the last waltz
- the concert for bangladesh
- woodstock
- many Mark's collaborations on other artists albums are worth listen, and have that Knopfler guitar sound : Bob dylan, John Illsley, Willy Deville, Steely Dan, Van Morrison, JohnFogerty, Tony Joe Wite,....
hope it helps