The Orion had the radar in the nose and the P-2 in a belly dome.What configuration is more plausible for the Comet?
Look at the Nimrod. And note how huge it's radome is and its double-lobbed fuselage. Remember, even though the Comet was a pure jet it's the older aircraft (it's first flight was something like 1947 or so) and so it held onto a lot of older engineering principles, including a smaller-diameter fuselage (back when it was assumed passenger travel would be relatively infrequent still).
Also, a belly dome
always contributes more drag. The reason why the P-2 had it was because it had an observer in the nose - the radar was a later addition because this is basically a WWII bomber.
That depends of the volume of radar is important,the APS-80 or the AVS-21D (that of Nimrod).
Well keep in mind that the canceled AEW Nimrod variant had (huge) nose and tail radomes.
Another "civilian" aircraft converted to MPA role was the CP-107 Argus (or CL-44 Yukon).How did this can help?
...how did this can help?
The CP-107 was a specialized variant of the CL-44 ultimately. It
did have a glass nose because it was felt that having a visual observer was important (with modern technology that is simply not true unless a SAR role is highly important, and even then you can just have a bubble window off to the side). It also had piston engines instead of turboprops because they wanted a more fuel-efficient plane (this was more or less sound, especially at the low altitudes MPAs fly at). But either way is unlikely to persist anymore - piston engines are prohibitive in maintenance manhours except for a very small plane and I already covered glass noses.