OK, a little update. Moving the engine back made my tall valve covers touch the brake booster. Dodge used a smaller brake booster on 3/4 & 1 ton trucks---as well as 440 trucks. Mine being an '85 required using a 3/4 ton booster as there are no big blocks for this year. While the small booster is better, i thought there was some roome for improvement. Here are the pics of the mods i did to move my small brake booster up about another 1/2" or so.
First step is to slot the bolt holes and the main center hole upward. You can only go so far on the bolt holes due to where the nuts are on the inside--they hit the bottom of the cowl. I actually raised the center hole a little too far, but the gasket still seals it fine.
I installed the booster, installed the top nuts to snug and backed off about a turn. I then pushed it up and tightened the top nuts (no easy feat to do under the dash with two hands). In this pic, you can see how much higher the studs now sit.
To make sure the move stays there, and to facilitate easier replacement in the future, i first place washers on the bottom studs only. I then tacked the washers to the firewall. I removed the booster and tacked them a few more times. I ground the surface of the washer flat again, reinstalled the booster and tightened all 4 nuts.
Like i said before, it was a minimal gain and it took some time to do, but i'll take that extra approx 1/2" gain away from the valve cover---on top of what i gained using the small booster--which was about an 1".