Before my buddy spends a bunch more money on his motor, I'd like to help
him optimize his current setup.  He's redoing most of the body this
winter, so it's not like he's afraid to spend the money, but his goals
are fairly modest.
(you can see it at www.rollingviolation.com/rv103 )

Currently, the car does the quarter in 15.27@89 mph.
He wants to do a 13 flat.  (basically, he wants to be faster than my
Trans Am.)

The car was originally a 6 cyl with a 'glide, and it doesn't have a posi
either.

The motor is from a 76 Malibu. (350 Chevy...)
AFAIK original rings and pistons - probably 8ish:1 compression.
Not burning any oil, so they're still "good" - (for 31 year old parts.)
Crank is stock, cut 0.10 under.
Heads are 882's, no porting done.  Original valves.
Springs were replaced a couple of years ago - IIRC with a Comp Cams set.
Used to float the valves around 5000, now it's good to about 5800 which
is about as high as he'll rev it. (We didn't measure the installed
height, so they'll need to be pulled and probably shimmed anyway.)
The dist is a Mallory HEI from Summit and he also has an MSD Digital 6+.
The cam is the old 447 lift 300hp 327 cam IIRC.  He has since bought a
Comp Cam cam with around 480 lift, but because the car has AC now it's
no minor job to swap the cam.
The carb is a Holley 600 (not sure of the model #, but it has vacuum
secondaries and isn't a double pumper.)
The intake is a Performer RPM.
Exhaust is a set of headers and no name mufflers.  (they're old, and
dunno the brand of headers.)
Holley electric fuel pump.

The TH350 is stock except for a ~2000 rpm stall TQ.
The rear is stock open diff, and we can't agree on the gears in there
and he won't pull the cover.  (they're definitely NOT 4.10's.)

The car pulls decent from the line, but is no torque monster, comes
alive around 3500 and pulls to about 5500.  Pulls about a 2.1 60 foot
time on a set of drag radials.

He's talking about a set of Edelbrock heads, but before doing that, I'm
wondering what suggestions I can make...

The first time we went drag racing it staggered to a 17 second run, and
we've knocked 2 seconds off just by tuning the car and Darren learning
to drive it.

Here's what I was thinking:
Spend $100 on a couple of dyno runs to see what kind of power the car
currently makes.  (I think he needs to wind it out more, especially with
that cam.)
More timing.  34-36 total.  Can't remember what he's got, but I bet it's
not enough.
I can see this taking a couple of tenths off, but not a full 2 seconds.
He keeps wanting to mess with the carb, and I'm no carb guy, but
wouldn't power valves and stuff be not really relevant at the drag strip
once your foot is to the floor?

I keep suggesting that with the stock low compression that he finds a
6-71 blower on Ebay, but he doesn't want it sticking through the hood.

How much more speed do you guys think is in this combo?  14.5?  14.0?

For $1500 what would get him the biggest HP gain?  (Nitrous
notwithstanding... worked for my car, but he's worried about blowing his
motor to bits with that.  I say he's a pussy.)

Ray