Sean,

 For reliable HP increase this is what I have done.

Add counterweights to the crank- reduces crank flex and doubles bearing life
Add a racing crank spacer
Fully balance ALL rotating parts
Rebuild rods lower end, re-bush and balance
Have WebCam regrind your cam to #91- increases top end power
Add solid rocker shafts
Add 1.25 ratio rockers: increase bottom end torque
Add Rhino swivel rocker tips: eliminated valve guide wear
Add Cromoly cut to fit push rods
Add Cromoly valve spring retainers
Have 3 angle cut on valve seats and 2 angle cut on valves.
Blue print a new stock oil pump: match the ports to the engine case:
increases oil volume.
Add a DynoMax Super Turbo muffler: It reduces back pressure (too much of a
reduction causes the engine to LOSE low end power) It fit in the stock
location with minimal modifications and it is QUIET at 80 mph. (I had a bug
with a loud muffler and after a long trip my ears were ringing, now with a
DST after trip my ears do not ring)

Match port the intake, exhaust.
Clean up head intake and exhaust ports- you can increase size slightly- (but
the larger you go the less low end power you have)

Clean ALL parts at least four times with the last with dish washing soap and
spray with WD-40 and wrap in wax paper until used.

THE number one reason rebuilt engine DO NOT last as long as new is because
the engines were not properly cleaned.

Apply some type of aluminum protector to the heads to serve as a barrier to
corrosion.
I chose ceramic coatings to add a thermal barrier also.

All the changes will give you @ a 30HP+ increase.

You can add the ECU chip at the end if you want a bit more power.

I also added a South African 5 speed tranny.  It is a bolt in, requiring only
a shortened front mount. I am using the stock linkage and simply push down
and pull back for first.  I like where first is because you can get to first
and reverse quickly to rock your van out if you get stuck, I did...  The
gearing is well suited to the power band of the engine.  In fourth I can go
to 75 mph if needed for passing.  I would not change the ratios.

I know it all works because I am driving it.

Robert