Do you want oil pressure to your rods full time or not?
I do , I use the ruck narrow full groove main bearings, not the wide full groove race bearings

Oil does two things in our motors, lubricate and cool, I like cool cranks

Are those the same as the MS-1277HG Clevite 77's?

I can't answer that sorry. I use to use the Seal Power part number M4500 for the RB motors and their M4400 for the B motors, I think they discontinued the M 4400 several years back
I prefer to build the 400 blocks over the 440 blocks due to the thicker main webbing

According to Mahle-Aftermarket's documentation, 3/4 groove bearings promote less HP loss and don't suffer any lubrication loss vs. Full Groove bearings.

Is there any reason to not use 3/4 groove bearings in a BB Mopar stroker engine? Or any better reason(s) to use Full Groove instead of the 3/4-groove?

Man, that's awesome! Glad they held up that well for you!

Yeah, guess I should have said RB based stroker...

Various forms of main bearing grooving have been used over the years. We are frequently asked what difference grooving makes. First, it’s essential to understand that bearings depend on a film of oil to keep them separated from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on wet pavement. Grooving in a bearing acts like tread in a tire to break up the oil film. While you want your tires to grip the road, you don’t want your bearings to grip the shaft. The primary reason for having any grooving in a main bearing is to provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be sufficient to lubricate a main bearing. Many early engines used full grooved bearings and some even used multiple grooves. As engine and bearing technology developed, bearing grooving was removed from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on. This provides a greater safety margin and improved bearing life. Upper main shells, which see lower loads than the lowers, have retained a groove to supply the connecting rods with oil. In an effort to develop the best possible main bearing designs for performance engines, we’ve investigated the effects of main bearing grooving on bearing performance. The graphs illustrate that a simple 180-degree groove in the upper main shell is still the best overall design. While a slightly shorter groove of 140 degrees provides a marginal gain, most of the benefit is to the upper shell, which doesn’t need improvement. On the other hand, extending the groove into the lower half, even as little as 20 degrees at each parting line (220 degrees in total), takes away from upper bearing performance without providing any benefit to the lower half. It’s also interesting to note that as groove length increases so do horsepower loss and peak oil film pressure which is transmitted directly to the bearing.

Here is the info from Clevite with the attached Graphs

I use 3/4 groove if I can find them. Sometimes it is really hard to find bearings these days so you just live with what you can get. In the old days when parts were available we used 3/4 groove on everything.

Is that a bad thing? What is your vertical clearance?

Bearings can be hard to find these days so you should feel lucky that you have a couple of sets to pick from.

I don't have a crank to calculate actual clearance but If I get a crank at nominal diameter than clearance will be .0025-.003( .003 on the center thrust main) . If I base it on the last K1 crank I had(main journals were slightly below min spec) than my clearance will be .0035-.004 (.004 on the center thrust main).
I had a set of full groove Clevite 877P bearings and mounted one in the #1 main to spot check and was pretty much the same.

AG.

Taken from the Cleveite bearing catalogue

“The wall is thickest at 90 degrees from the split and drops off a prescribed amount toward each parting line, depending on the bearings intended application. This drop off is called “Eccentricity.” In addition, there is a relief at the parting lines. Eccentricity is used to tailor the bearing shell to its mating hardware and to provide for hardware deflections in operation. Eccentricity also helps to promote oil film formation by providing a wedge shape in the clearance space. The relief at each parting line insures that there will not be a step at the split line due to bearing cap shift or the mating of bearing shells that differ slightly in thickness within allowed tolerance limits”
Its a good read if you want to know bearing specifics..

I've noticed the same thing, any idea why?