I am buying a M4 upper to make a M4gery.

I am trying to decide which one of my preban Colts I should use. I have a Colt SP1 with the triangular handguards and a Colt 6520 government carbine. Both lowers are slab side with no sear block. I have a Colt collapsible stock on hand for the Colt SP1 if I go that route.

If I convert the SP1, I still have a postban bushie 20" to take it's place.  

Tyler, thanks for your input. I may lean toward the SP1 since the finish on it is blacker than my 6520 (which is gray). I think that the Colt M4 upper is black though probably not the same shade as my SP1.

BTW, who is this Miko person?