I'm going to build a lower that needs a large hole to accomidate a Colt SP-1 upper.  I al;so have several other uppers with small holes that I use those adaptors to attatch..  I don't care to pay for the Colt name and I'm Not famiiliar with what's out there for sale and I 'm not familliar with the pros or cons of either milled or forged including price.  Also where do you buy these things???  The Old Top needs advise!!!  THANX--MSGTGENO

Offset pins are avaliable for purchase that allow you to use large hole uppers with small hole lowers and vice versa.

Link to offset bushing that allows large pin upper installation on small pin lowers

Welcome aboard msgtGENO!

Colt was the only one who made uppers and lowers that used the large hole. So if you don't want to spend the money on a Colt lower then you're going to have to use the bushings the other guys are talking about.

Quoted: Link to offset bushing that allows large pin upper installation on small pin lowers

Once again, mongo got it exactly right

You'll notice that the hole in the sleeve is off center. When you mount the thing, start w/the thin side at the top of the hole in the upper. You may have to adjust it slightly forward or back to get the upper/lower fit even. Once you do, cement the sleeve in place, and you now have a "small hole" upper that'll fit any current production lower

The old Top here:  Thanx to everyone for the come-back.  I decided from your advise to sleve the SP-1 upper and I decided to go with The Anvil Arms stripped lower--Price is rite, Looks good and clean on their web-site (Yes I realize that it is the internet and anything goes) and the possibility of FREE(as in NO-CHARGE) custom lazer engraving makes my mouth water with the possbilities.  Plus, they are just down the road from my son in Lakeland.  And their price for a "Complete Parts Kit" on sail( I'm from the Keys)=$55.00 which I'm ordering.  I'm going to scrap that trigger and Install a JP Enterprises adjustable trigger.  I'v got a JP on the SP-1 lower and it is sweet.  I'll eventially let you all know how it goes when it's done (1-2 months--I'm retired and lazy from dodging all these Hurricanes lately).  THANX--msgtGENO