377 or 421???

[hipower17]

511 are junk

[Jim11h]

2 bolt allows you to have splayed caps which take the stress better then a "true" 4 bolt block. 6" rod reduces stress internally as well and these items cost but add to longevity

[fastford]

the longer rod extends piston dwell , it stays at the top longer , which helps with higher rpm power , this is more common with the shorter stroke 377 combo because you are normally turning it more with the destroked combination , the longer rod also decreases rod to stroke ratio which usually extends piston life , if you dont have good enough stuff to turn high rpm,s , then i prefer the shorter rod to help with torque off the corner. I have a 302 ford block with a 3.5 stroke and 5.4inch rods , its a beast off the corner but is rough on pistons.....also Jim is correct above , we just done a 4 bolt conversion on the three center mains , this is way better than the original 4bolt block , but expensive , your about as well off to find an aftermarket block , like i said above , a half fill with moroso hard block is inexpensive and really strengthens the block.......