well there are variations as well,
second generation PEI (low center of gravity), its basically the same as the PEI posted above, but the cradle allows the engine and drivetrain to sit lower.
Cohens are what the CRD's are based off of, Tim Carroll (of Carroll Racing Development) went to the digger dugeon and actually took measurements off of Adam Andersons chassis (which was Taz at that time).
Cohen's (or inhouse chassis's) started with Dennis's digger 19/20
Then Adam's truck was made
but there is a second generation of Cohens, Son Uva Digger, Grave Digger 25 (Gary Porters new one) and Monster Energy
SUD/GD25
Monster Energy
But then there is a interesting itteration that is a mutant, when Alex Blackwell stuffed Captains Curse into the stands at WF10 it was rebuilt, it started as first generation PEI with a Race Source Cab area (this was to fit the willy's body). When it was rebuilt it was built with some Cohen specing, mostly the shock towers cab to shock tower bracing and cradle bracing