Did A Compression Test Yesterday...

[Jim300D]

I picked up a '78 300D from a friend of mine for cheap exactly a year ago. Since then I've put some TLC into her but haven't invested too much yet because I wanted to do a physical on the motor first. Well I finally got around to doing it last night after I gathered all the tools to do so. I did a valve adjustment a week ago and have driven the car maybe 100 miles prior to this compression test.

The compression test was performed about an hour after driving home from work (engine reached full operating temp).

These are the maximum numbers reached:

Cyl.
#1 - 280psi
#2 - 340psi
#3 - 325psi
#4 - 359psi
#5 - 275psi

Not the results I was hoping to see exactly. The car has 170k on the clock. 3 out of the 5 cylinders have fairly good compression. I plan on doing a leakdown next to determine the cause of low comp. on cylinders 1 & 5.

My thoughts are this: because of the relatively low mileage and the healthy #'s on 2-4, it's my hopeful guess that the valves have carbon on them and are not sealing well on 1 & 5. Especially since I have no idea the last time the valves were ever adjusted.
If that proves to be the case, how much effort is it to pull the head and do a valve job? What does a valve job typically run for these heads? Maybe it only needs a good cleaning? Just trying to figure out if it's worth continuing on with this project car. I was going to rebuild my injectors, replace timing chain, and set IP timing if the compression test checked out, now I'm not so sure...

Thanks guys.