Geeze - it was just an example of something that can work - a clip in part. 
Most guys that want to run a factory head without spring pocket modification are going for lower dollar budget stuff.
Something you can do "at home".
You can play with the pressures a bit with spring seats and offset keepers.
But you can't go too far before you run out of "step" as a locator.
If you want to get all fancy and stuff there are lots of "better" choices, but they involve spring pocket cutting and such.

A PAC 1220 beehive will fit nicely on that OEM step, and with a .030 shim and the appropriate retainer and keeper combination should get you around 140ish on the seat.  Not race car stuff but given the light weight of the retainer it should be perfectly fine for a street hydraulic roller deal.  I am not normally a big fan of single springs (like the beehive), but this is a case where they are the best solution for the problem and I have done many using this combination without any issues at all.

So it seems Brian Nutter is the guy designing the lobes.(cant find a ton about him)

Brian is a very sharp dude.  He has a lot of years in the industry - although little direct FE experience.
H put in a lot of time at Wiseco doing pistons before moving to Summit.

We can get further into the "weeds" on this stuff by adding in the impact of "hoop stress" from the bearing shells.
An installed bearing pair is essentially a press fit, which we observe as "crush" - the amount of bearing shell that sticks out of an unassembled housing bore.

At F-M our engineers (I am not an engineer) recognized the importance of increased press fit on performance bearings.  They saw greater dimensional integrity and enhanced heat transfer. To get that value, they increased the amount of crush.  When they increased the crush they had to change the type of backing steel used in the bearing shell because the standard material would buckle under the increased load.  That stronger steel and higher crush load will impact housing bore integrity.  Another reason to directly check bearing clearances as an assembly rather than simply stacking measurements.

After reading about Jay's casting challenges - and knowing that I might not be able to ever get another one of these - I am just gonna hang onto this for a while.
Sorry....

I will agree with the other guys for the most part.
But I also want to play "devil's advocate" for a moment as well.

When doing balance calculations - what do folks doing the work add to the equation for "oil"?
I have seen values anywhere from "nothing" to "10 grams".
I can pretty much guarantee that the value chosen is - in the vast majority of cases - based on nothing beyond legacy, opinion, or wild guess.
The guys at Ford or NASCAR probably know exact values - the rest of us take the best guess we can with available information.

And many balance folks will promote the accuracy of their balance to 1/4 of a gram.
I had the pleasure of digging into the software of a reasonably new, reasonably nice, and reasonably expensive balancer.
We discovered that it had a +/-3 gram fudge factor built in that would happily print out "zero" on the display.

I am NOT telling anyone that a poor job is OK, nor that anybody is misleading them.
I am telling folks not to get too freaked out if balance stuff is not perfect if/when they check it themselves.
The process catches outliers and gross errors/issues.  It gets things close.
The minutia can remain minutia without ill effects.

I have sold - and built - hundreds of FE engines with cast Scat cranks for over 20 years now. 
I have only had a few of them truly break. 
They were at or over the 700 HP level, or in continuous load applications - marine/road race.
Those guys - along with blower guys - simply require steel.  No option.
For everyone else it's insurance.

Thermostat makiing it worse might be the clue.  Points toward Jay's comment about coolant flow - water pump.
is this a "new build" or something that has been running for a long time?
I have seen engines that got hot very quickly on dyno when head gasket was installed backwards.