I am in  the process of gathering parts for my new project, building a correct CAR-15 upper for my 1981 Colt SP-1 rifle. I know that I won't be able to find the correct 1-12 16" carbine barrel, Hoplite and J&T both have new 1-9 Colt barrels for around $250. I have a perfect non forward assist large hole upper that I found at a local gunshow, perfect match to the color on my lower, only it's not marked with "C M" under the rear sight drum, so I don't know if it is Colt or not. I have the correct flat delta ring assem. Did early SP-1 carbines have a 2 position collaspable stock? I am going to purchase a new complete bolt assem, can I use a new style Colt bolt that has the complete rear machined off, or do I need to get a Bushmaster that is only part machined like my SP-1 has now, SP-1 has the older style trigger assem with the small pins like the Bushmasters.
Last question, were the early SP-1 cabine handguards much different than the current production ones, I know the M-4 handguards I have on my Bushy are a much smoother black finish than the factory rough finish.
Thanks
Mark

The early Colt SP stock was open or closed. There were no intermediate stops like the new M4 model.
You should be able to use either bolt carrier.
My early SP had guards that looked like the newer guards.

Your upper sounds like a Colt.  There weren't too many other companies that would make a large hole, no-FA, Colt color upper.  The 1/9 barrel will let you shoot any ammo, so you're ahead there.  The two postion buttstock was also aluminum covered with teflon.  Not a fiberlite or plastic.  You'll probably be able to just use your current bolt and carrier.  Once you get your barrel, check the headspace with the SP-1 bolt.  If it's good you can just use it and save $100.  The handguards are just the basic round CAR handguards.  I seem to remember mine as being shinny black.  They aren't M4 ones, as they are fatter.  Also they did have liners.  Many of the aftermarket CAR handguards available back then (early 80's) didn't have liners, and were just plastic.  They got way hot, way fast.  The real ones were shinny, black with liners.

Ross