After checking out my whole fuel system I finially found my mechanical fuel pump was not getting the full stroke & my fuel pressure was dropping off as the revs/load increased.
6-psi @ idle & light load, down to almost 0-psi @ 5000rpm & heavy load.
My main problem now is getting the plug out so I can replace the pushrod, it won't move at all, how does everyone else get them out?

If your fuel pump has been lagging, maybe the pushrod that drives it has gone bad. I have heard that high miler big blocks have actually mushroomed the pushrod at the cam end! The only way to get them out is to pull the cam. Then you have to push the pushrod in further and take a file to remove the flared out end. Once it has been filed down enough, it should back out.
If you cant pull the pushrod out with a strong magnet, you may have to pull the timing cover to take a look.

It's the threaded plug that I can't get out, it won't move at all even with a few good whacks on the end , WD40 & a good long allen key!

Sorry I misread your post. Have you tried a hand held impact driver? I had to use one when removing gallery plugs held in place with "Gorilla Snot".

Na, didn't think of an impact wrench, the hex may be a bit past that now but I'll give it a go at the weekend.
We only have one quarter mile event in our city each year, my converter went bad so I took a couple a days off work, changed it out & did some other things to get the car ready. When I took it ('70 383 Barracuda)out for a quick test run it surged at about 5K, although it felt like a lack of fuel my LM2 didn't go lean every time it surged but hooking up a fuel pressure gauge above the hood sure showed the problem. If I had of thought of the pushrod before I replaced most of the fuel system I may have been racing tonight!

I just went thru this. I took a grade 8 bolt and used a belt sander to grind to fit the plug. Tapped it in and eased it out.

Put a breaker bar on that allen wrench and shock it (like you are doing) rather than a gradual pull

Mine had a square hole, allen wouldn't work.

Thanks guys, I'll give those things a go, Cheers

KROIL KROIL KROIL...Soak,tap with hammer, repeat.
Kroil is unbelieveably better than W-D 40 or ANY others on the market.

Plug came out after soaking overnight and some more
Can't believe how much pushrod is worn
Both ends were worn hollow, .018" deep on the cam end & .022" on the pump end.
There was major wear on the cam end leaving an effective pushrod length of only 2.874" which is .368" shorter than the MP P529569 pushrod ( 3.242")
I measured the travel of the cam lobe & it measures within 2% of a new Comp cam I have to compare it with so I'm not replacing the cam at this stage, just the pushrod.

Cheers for your ideas.

Keep an eye on the problem. ALL cam lobes are hardened at the same time. Ever have a cam go flat? The "Parkerizing" process is the term for camshaft surface hardening. It is similar to any other hardening treatment in that it only penetrates into the metal by a few thousandths of an inch. ANY measureable wear from a cam lobe will wear through the surface and into the softer core metal. From there it wears really fast. All the shavings and debris will fall into the pan, through the oil and hopefully get trapped into the filter. Some debris will get embedded into the rotors of the oil pump and some will get crammed into the crank and rod bearings. Stop before things get any worse!

Yep, I hear what you are saying
I have lost a lot of metal off the ends of my fuel pump pushrod over a period of time & as an engineer I do understand that there will be other damage caused by the "missimg" metal.
The engine is a low compression 383 that has been together & thrashed for quite a few years & although I change the oil & filter very often & drain the oil into a spotlessly clean drain tray so I can look for signs trouble, I had no idea so much metal was going in my oil.

Looks like it's time to dust off another block & built a better engine for when this one fails.