like Bushmaster and the older Colts?

thanks in advance

I don't know about Dalphon, as I've never used their products.

I've built AR's on the following lowers:

Bushmaster - A solid product with all the legal mispec features (oiling holes, forged, raised fence etc.)

Rock River Arms - Another solid product with all the legal milspec features.  RRA's are a bit "tight" until the upper and lower and the pivot and takedown pins wear in.

American Spirit Arms - An okay product.  These are forged, but without all of the milspec features (no little oiling holes).  I had trouble (canted pivot pin holes) with 2 out of the 4 that I ordered.  
DPMS Stainless - An okay product.  These are cast and certainly not milspec.  I had to clean out the grit from the pistol grip screw boring and actually rebore the pivot pin detent spring hole to standard length.  I also had trouble installing the 2 stage Jewell trigger.  There wasn't enough clearance in front of the hammer, so I had to rebate a section of the hammer.  Even with all of the fuss, it serves as a great basis for my high power match rifle.

Olympic Arms - An entry level product.  Some are cast and some are forged.  These do not have all of the milspec features.  I use cast Oly lowers to build canoe / truck beater rifles out of M&A kits.  

Hesse - Never again!

Colt - I never built a rifle on a Colt receiver but I do own Colts.  Most pre-bans are slab-sides.  Some have raised fences.  Some have sear blocks.  Some have that wierd honeycomb thing going on where the sear block used to be.  However, they all have the milspec oiling holes and are forged.

Hope this helps.