The MCarbo spring set is good - the Sear spring is a complex 'double-coil clothespin' sorta thing that'd be complicated to make. For the trigger return spring I just cut about 1/3 of a pen-spring instead of the MC one. got about 2# trigger. And I polished ALL the innerds with 1000g paper then spray with dri-lube silicone. On my newer 64 I have an El Paso Weaver D4, and the Amazon Reflex on the older one. Both are very reliable with 'low-cost' ammo and pretty accurate with CCI-SV or SK+.
