[Marq92]

I've heard of people not taking a low rpm hit from the 188/220 but I've also heard of several that did. For what you are looking for best possible fuel economy and highest efficiency I would lean towards the 178/208 which is made for that.

 

[Marq92]

Also with the 67mm wheel for towing at lower rpm you're not going to be happy.

 

[Marq92]

I'm sure that Hamilton can set you up with a roller cam. There is a also No Limit Manufacturing that sells flat tappet and roller cam, and you might be thinking about Wagler for their solid lifter conversion for the 2019+ trucks with roller cams. I would definitely avoid fly cutting the pistons to clear for a large cam for this application but you could get a custom roller cam in the smaller sizes that the flat tappet cams come in would just cost what the roller cams run ~$850-950. Then the roller lifters which I haven't seen prices on.