Strong points are as follows:

Any crank will fit into any block.
(Clearancing required to put 401 or 390 cranks in the 290 or 304 blocks)

Easily converted to use a Milodon single line oil pickup.

Also availible is the Milodon dual line pickup.
(This will double the oil volume from 5-6 gph to 10-12 gph!)

It is recommended that the Milodon deep sump oil pan be used. It holds 7 qts. And is a direct bolt in for the swivel pickup that comes with the pickup kits.

The various overbore capabilities allow the use of many different pistons.
ie. Chevy 305 pistons fit in a 304 block to give you 311 ci.
Chevy 400 pistons fit in a 360 block, and while this only gives you 367.7 ci., this combination with a 401 crank gives you a 393.4 ci.
Many more combinations are availible.
Please note that these combos are with machine work, and are not just drop in.

Large lifter bore sizes allow for more choices in cam profiles. And give better lifter cooling capabilities at lower rpm, and a larger contact patch for the cam lobe. Meaning that the lifters can support a more radical grind without special machine work or be able to sustain higher rpm usage.
While this seems unimportant to most 4 wheelin, it does make a BIG difference when trying to use a roller cam because of the much more aggresive profile.

Large valves. The 360 and larger heads came with 2.02 intake and 1.685 exhaust valves. Also if one wants to have a motor that will turn some higher RPM's, then it is easy to use a 11/32" vavle stem instead of the stock 3/8". This allows for higher RPM, and the reduced weight will benifit the horsepower numbers. Chevy valves are almost direct drop-ins in this case.
Another note is that with minor port work, it will bring a much better flow rate.
Hope to have some actual numbers to back this up soon.

All the blocks use the same mounts, manifolds, covers, and accessories. About the only thing that that is difficult to use is 360 or larger heads on 304 or 290 blocks. The bore difference with the larger valves (304's had 1.74 int. and 1.405 exh.), mean that the block will need some machine work for clearancing.
Note that the use of 390 and 401 heads are preferred because of the larger exhaust manifold bolts, and the rocker studs are already tapped for 7/16" studs. Meaning that you can simply get 7/16" studs and roller rockers, different pushrods, and some Isky adjustable guide plates. Instead of either using the 'KIT' that still uses the 5/16" stud which is weak. Or having the heads machined to accept 7/16" studs, and machined down to fit the guide plates. Finding a good set isn't easy, but saves on the money you'll spend on machine work.