Coolant passage?

[welpro222]

Whats the different block cooling passages about? I have a 83 blazer 6.2 that has the rear cooling passages blocked and the front open and i have a 1991 suburban 6.2 that has the front blocked and the rear open?

Is one better then the other block?

 

[hre513]

 

[welpro222]

My block looks like this one. Blocked coolant paasage in front of piston #1 and open in rear of piston #7. This is opposite in my 83 blazer, open front and blocked rear.