The first Pic of the SR (or replica SR ) that Marc has posted is very simillar to the KX 250 Brad lackey is riding in his book motocross techniques , training & tactics by Brad Lackey and Len Weed.
Those of you that have a copy check out pages 68, 69, 80 , 81, 108 & 109 , the bike has the Bannana swinging arm and the muffler exiting the RHS .
Tank and seat appear to be std A5 items and side panels are A4 i cant make out the forks
Pages 66 & 67 brads riding a std A5 , maybe the other bike is a pre production A5