I am trying to put some engines back together. I have a Mark IV crank and Gen VI block, pan, front cover, and Mark IV heads.

Can I run this package together and if so what would I do for the rear main seal?

Thanks for the help

There are a few companies which make an adapter to run the
mkiv crank in the gen vi block.... Take a look at the Competition Products website

Mark IV heads will probably be an issue.

The coolant transfer holes on the Mark 6 block were revised from Mark 5, the 6 holes should be small round holes to accept Mark 4 heads, so the heads shouldn't be an issue either. Is the 6 a Bowtie? Even my Mark 5 bowtie has round coolant holes so the Mark 4 heads work well. I have always run the Mark 4 crank with an adapter and no problem. Just be sure when you install the adapter that when you sela it in, let the sealant dry then torque or you will have a leak.

you cant use a markIV crankshaft in a gen VI block,it would be impossible to get the 1 piece rear main seal over the rear counter weight on the crank.. look on ebay for a forged crankshaft,i see them all the time for 200-400 bucks..you will also need a flywheel for a gen 6 as well..

I know that adapter works with gen V. Don't know about gen VI??

Ben IV heads, no problem. Make sure you use the good marine fel pro gasket.

Good luck and keep us posted

The crank will work fine. I have a adapter I can hook you up with. It is at the machine shop with my ruined block. I will pick it up this week and I can send it too you. You will need a gen 6 pan and timing cover still. You will use a two piece rear main with the adapter.

Are the heads aftermarket or GM? Most aftermarket heads are designed to work fine with any type block, you just have to use the correct head gaskets for the block.

thease leaky things?

http://www.stefs.com/catalog/30rearsealadapters.pdf

Yep, ran them without a problem.