Re: Relatively easy question for most anyone
This relatively easy question eludes alot of designers and car builders. Most of these front engined cars actually still have more weight in the rear. A lot of them have aluminum engines and there are several components moved back to shift weight to the rear. The heaviest component on the vehicle is the full fuel cell. These often weigh more than the engine. It is common to house the fuel cell entirely behind the rear axle centerline. Batteries are at or near the back of the chassis. Radiator(s) are in the "back window" of the roll cage, dry sump tanks are moved back. Most Trophy Trucks carry 2 full size spares behind the fuel cell. There have been TT's with water pumps in the rear and steering boxes mounted behind the seats (Ragland's earlier TT).
To make a long story short there is considerably more weight in the rear. Most TT drivers will tell you their vehicle rides better with a load of fuel onboard. The latest trend is a backward facing "mid" engine location and a boat V-drive near the co-driver's feet (Ragland, RG). This makes things easier to balance but does not save any weight.
As far as the speed factor, most of it was answered above, but there is also the tremendous suspension available. The TTs arguably outpace all others in a straight line. Unfortunately they don't handle that well and are not as agile as most Class 1 "buggy" type cars. The supersoft, long travel suspension provides a lot of weight transfer. This greatly helps traction and also let's them have tremendous stopping power.
Lastly, these vehicles are not light by any means. Most TTs are over 5,000 pounds! When someone does build a light vehicle of the same design they usually don't work well. Unsprung weight of 500 pounds or more (rear axle with wheels, brakes, etc) is too much for a 3500 pound vehicle but just fine on one of 6500 pounds. So far, the disadvantages of 4WD or AWD outweigh (literally) the advantages. It works for rally cars but the best of them would never complete a lap at speed in the desert.
Hope this helps at least a little.