<VV> Where do I go from here?

[Jack & Elaine Kean]

I purchased my current car (1968 Monza Convertible
with 140, 4 speed, 3:27, Corsa dash) last summer. It
had around 2000 miles on the current rebuilt engine.
The motor ran fine, with good performance and very
little oil consumption. The only noticeable problem
was the excessive valve clatter, which I attributed to
incorrect push rod lengths, when I purchased the car. 
Since then, I put around 1000 city miles on the car
with no real problems, except the engine seemed to run
hot, even though the cylinder head temperature never
read much above 400 degrees.

One afternoon, the clatter became noticeably louder on
the drivers side, so I attempted to adjust the
valves. This was an attempt to see what was going on.
This is also when the real problems began. The
noisiest valve clatter seemed to originating from the
#6 intake valve. I listened for a while, and then
adjusted those three cylinders while the engine was
running. However, the clatter was still there. I then
pulled the rocker arm and saw a fair amount of wear on
the top of the valve stem, indicative (I think) of
push rods that are too long. After I reassembled the
rocker, and readjusted it, the engine runs rough, and
clatters. It occasionally backfires. 

I have not driven the car since, and wonder what the
most reasonable course of action would be. 

-	Should I determine the correct pushrod lengths,
install the proper pushrods and see what happens?
-	Have I messed up this lifter?
o	Should I simply replace it and see what happens?
-	Do I have a dropped valve seat (the miss is not
constant, and all three cylinders have reasonable
compression when I checked them last)?
-	The sparkplugs are sooty. Could I have fouled them
because I let the car idle so long?
-	Or ???
I am only hesitant getting into this engine, because
it has been 14 years since I owned one of these cars. 

It is a kick to drive, and I only want to get it back
on the road soon.

thanks

jack kean