[russell_ram]

Christoff,

Yes it's possible but not easy.

Assuming you are going to use 4.0 or 4.6 rods to match the crank BE pins (which are much larger than 3.5), you will find that the B/Ends will foul the block during crank rotation and will need some serious relieving. How bad the fouls are depends on the age of the block.

By the time you have line bored the block to take the larger main pins there won't be much main cap thickness left. The later blocks have much deeper, X bolt mains caps. You risk durability issues in the caps - even factory small bearing 4.2s are marginal and commonly fail main cap 4.

Alternatively you can get the crank mains machined down to 3.5/3.9 size. Obviously this reduces the pin overlap and reduces the strength of the crank.

You have to use factory 4.0 or 4.6 or after market rods to match the bigger BE pin size. 3.5/3.9 ones aren't big enough to open out to the larger bearing size.

Next problem is that you won't have any of the std pistons to fit. The 3.5 pistons won't fit the 4.6 rods and the 4.0/4.6 pistons won't fit the 3.5 bore without a re-sleeve. (Using a 3.9 block would fix this problem though).

EASIEST bit is the front cover - you can use any of the available ones. ie SD1 by fitting a spacer in front of the crank pulley to take out the extra crank nose length, or any of the later LR concentric pump types using a later poly V/serpentine belt system with or without distributor.

HTH

Russ