What was the first year for hydraulic lifters in the /6? I want to build another motor for my 70 Valiant but I'd like to get away from solid lifters.

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70 Valiant Super Six

'81. The hydraulic head has a different shape than a solid one. There is a kickout behind the alternator that is not there on a solid.

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Official Cookie and Mater Tormentor.

the 1981-1987 slant six trucks all had the hydraulic lifters. Finding a complete motor out of a junkyard is the easy way to go.

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1980 Aspen 225 super six

The only problem with the hydro motors is the fact that the cams are very mild and performance cams are hard to come by.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Yeah, I can see wanting to go to hydro lifters in a super-cramped engine installation where adjusting the valves is a PITA—such as, coincidentally enough, in an '81-'87 car with all that emissions plumbing and widgetry in the way of removing the valve cover!—but in a regular installation, I prefer the solid lifters. Much wider cam selection, and it's not a bad thing to have to spend some time every now and then closely examining things under the hood.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Believe it or not, I have an Ultradyne for a hydraulic motor.

I have no clue what I'll ever do with it, but I gots one.

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Official Cookie and Mater Tormentor.

If youre not going racing and just want a slightly hotter cam they make them. They will even make custom grinds for not to much more.

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1966 Dart GT
4 spd. OD conversion
8 3/4 - 3.55 SG (Sold)

62 Lancer GT
B Body 8 3/4

I have one of the newer heads with hydraulic lifters on my '82 D150, and it is in desperate need of a valve job. Can I use one of the older heads that used solid lifters on my block? If so, what changes are required (aside from the cam and lifters, of course).

As far as I know, you can use a head from a solid lifter engine, just swap over the hydraulic lifter rocker shaft and rockers and keep all your hydraulic lifter parts on the engine. You will also need the valve cover from the solid lifter head. Do check if by chance the rearmost rocker shaft bolt is different between the head you might use and the one you have now.

The main difference between the "hydraulic" and "solid" lifter heads is that the "hydraulic" head was changed to allow removal of a bad hydraulic lifter through the head so you did not have to remove the head to replace a lifter. The valve lifters do not fit through the pushrod holes in the solid lifter head.

That all matches my understanding, but as I said in another thread, I haven't investigated the matter carefully.
...they do on the '74 and earlier plug-tube style heads!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Maybe I should rephrase my question: Can I convert my hydraulic lifter block to use mechanical lifters without considerable difficulty?

I believe the block is the same
Pretty sure, but not completely...

Yep, just drop in the parts, and it will work. (never done it, but i'm told)
Parts include,
cam
lifters
push rods
adjustable rockers

Basically, it's pretty easy if the motor is on a stand, but a big pain in the rear if you don't want to take the motor out of the car.

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1980 Aspen 225 super six