I'd never do a conversion like that since you'll most likely run into a bunch of interference issues down the road. The guys who build headers aren't expecting those big chunks of metal to be there for example and like you said, oil pump clearance will most likely be a problem.

I think the best way is to find a V8 K frame with the spool mounts and then move the mounts back like the factory did. When you do that you end up with an almost factory solution so headers fit and oil pans fit and all of that jazz. There are of course other solutions. You can use the earlier V8 K frame or cut the mounts off of that /6 K that you have and go with a motor plate.