I wouldn't know, but I wouldn't switch the wire harness to a newer one. That's just asking for problems.
Heres an idea though.
Why not remove the valve covers, rockers, and push rods.
See if the holes in the push rods are plugged. You probably know better than I do that you should be able to just blow through them.
Use a Turkey Baster to fill the lifters as much as possible.
And then use a screwdriver or something to try pumping up the lifter (I really recomend a wooden dowl if possible).
If it works you might have to add more oil and continue to pump them for a little while longer.
The most that it will cost you is some time, and gaskets that you'd still need to do that job you had planned + a little oil.