1991 4.0L OHV Aerostar. Lifter & pushrod questions.

My aerostar went down hard, water in oil, after coolant loss. The engine is out now, replacement heads due any day. The engine history, prior to losing the heads, is 55K on a Ford dealership longblock. The block deck is flat, so the the engine should have considerable life; we plan to fix the heads and put it back in, with existing pistons, cam and bearings

Reading the posts here, I thought to replace the pushrods, in the belief that the upper end is poorly lubricated and prone to wear. On a quick inspection of several, I don't see obvious wear, but I do see the pushrods are solid, not the hollow oil-movers i've worked with on GM and Chrysler engines.

I'm interested in pushrod input, but more important and expensive is the hydraulic roller lifters.

My mechanic wants to replace all 12 lifters, which run $20-50 each. I figure the Ford longblock lifters are better quality than the lower priced lifters, and ought to be worth cleaning up, or at least disassembling to inspect for water damage and carbon.

The pushrod Ford buff at Autozone showed me cutaway pics of hidden inner-wall chambers in this vintage lifter that are impossible to decarbonize, leading to a high risk of soaking it loose in a way that will fail the lifter after the engine is run. So his thought is either replace them without decarbonizing, or bite the bullet and replace them.

What's the lifter-wisdom here? I just watched a convincing (I know, right?) Youtube recondition job on 91-94 4.0L Ford lifters. So there does seem to be uncertainty on the clean or replace question.

I should mention that this is a rare unit, a Chinook pop-top camper van That's why I bought it, and why I would consider the cost of parts and mechanic to revive a 91 Aerostar. You can see exterior pics at this thread:

http://www.explorerforum.com/forums/showthread.php?t=431061

I cleaned mine.
I did have 2 sets of lifters. I broke some of the plastic caps that the push rod sits in trying to get the right technique to remove them for cleaniing underneath.

I don't remember seeing any hidden oil chambers, but it was quite tedious and if the motor hasn't seen regular oil changes, I'd replace the lifters. The donor motor I was using hadn't seen oil changes, and the lifters were brutal.

pushrod lifter design, clean/refurb video

This youtube video is helpful; the procedure and his simple tool innovation is solid, even if the camera work is a static wide shot.

https://www.youtube.com/watch?v=xfx0-iGaUpA

I wouldn't want to worry 12 lifters apart without detailed instructions, compressed air and a soccor ball inflation needle threaded into the high pressure nozzle tool, as shown. Even with these advantages, It took me all day, and I was unable to dislodge one check valve cylinder from the bore. I'll have to replace that lifter

My 91 lifters are a double-wall design, with a cylindrical oil chamber between that can only be cleaned indirectly and imperfectly, thru the small oil distribution ports. A pushrod Ford nut at Autozone was able to pull up a cutaway picture. Good light and reading glasses also recommended.

As you say Dono, if the lifters are sludged from unchanged dirty oil, soak-loosened varnish and carbon may linger in this hidey-hole, and come out to foul the check valve. Knock on wood. The plastic oil funnels can be pried up from underneath in four places, with a very small screwdriver, with minimal risk of cracking them. But watch out for that eeensy check ball spring; it's nearly invisible