300 inline 6 head replacement
 

I'm looking to swap out my head for a rebuilt one with hardened seats, does this engine have hydraulic lifters, and if so does that mean no valve adjustment needed only torque rocker bolts at install? Or is this more involved than a evening job?

They are hydraulic, but they do need to be adjusted.

I'm no 6cyl. person but I think they all had hydraulic lifters. As far hardened seats I don't think you need those in an engine with only 8.4-1 compression. I have taken a bunch of old Ford engines apart and the only one I came across with serious seat recession was a 429 Cobra Jet that had been driven by teenagers putting the cheapest gas they could find in it. Even then I felt it was the 11.3-1 compression combined with cheap gas that caused the problem. If you feel you just got to have hard seats just take your head to the machine shop and have them rebuild it. I just got a set of 4 barrel Cleveland heads back from the machine shop where I had them install new seats, not because they had recessed but because three of them were cracked. It was only $120 for all eight exhaust seats.
I'm sure some of the 6cyl. guys will chime in on what will fit your block.

Some 300's had adjustable rockers and some didn't. I don't remember when they changed. Either work fine, but don't mix parts between the 2 types.
Actually, you should ask on the six cylinder forum here.

How do you adjust them?
 

With the valve cover off and tighten the bolts I'm guessing, or is it by changing the rod lengths, heard the valve cover off method can be a bit messy

Idle it as slow as you can, lay a couple of shop rags across the top to keep the spatter down and it should be fine.