harrym,
the Beverley's cargo compartment was higher than that of the C130K at 10 feet. The C130's was just over nine feet with lots of kit in the 'hog trough' being a limiting factor. Plus the Beverley had the boom which could carry pax and paras leaving downstairs available for pax and or cargo.
The clamshell doors were a limitation which was an inferior solution to the C130 ramp and door. The C130 cargo compartment dimensions were based on the standard US railway box car.
I think the achilles heel of the Beverley was the Bristol Centaurus engine which as harrym has implied were thrashed to death doing a task for which they were not intended. The Allison T56 turboprop in the C130 was in many ways the making of the a/c as it could not have achieved the same level of performance with piston engines.
On the subject of carrying portable radar I once took one to Biggin Hill for one of their air days. A long time ago but I remember it was a tight fit !