What aspect of the plant would you like to improve on? Not frosty enough? Not enough weight? Height? Spacing?
If it's a relatively "pure" strain, I'd look for the same purity but with opposite characteristics. The early flower pic doesn't show enough info, but if it's relatively spindly and tall I would shoot for a pure Afghan that's squat and bushy, etc.
Hey I just say your post in another thread about RE, I posted before you about cloning success in Rapid Rooters...glad to see someone else can do it to, I just don't get all the fuss about aerocloners, rooters are soooo much easier...so I looked at your profile and saw this thread and came to look at this one...that is so funny, my second big grow and first grow with CO2 I used seeds from Oaxacan and Diesel cross and MAN, we laughingly refer to it now over beers as "the jungle grow"....LOL...it was hilarious, it was in a back bedroom, about 12 x 11 and these dudes went right for the sky, or rather ceiling, we ended up having to bend some of the cola's in an almost complete circle...the smallest cola's were as big as my forearm (normal guy sized), and oh wow, just the memory of it is making me laugh...We got so much killer herb...but they got a little light cycle mix up and they hermied really easy..that was the worst, trying to find them all, which we did...anyway I saw this post on your profile and thought i would say hi.....so hi! Oh, and I still have some of those seeds somewhere, i am just too intimidated by them i think...haha