Thats right...don't. By the time you get it modded up to have some decent power, well you will have spent some realllll money. Short of the turbo or supercharger route you are going to be into it big time!
This is coming to you from someone who spent a few thou to get my 5.9 to move and in the end still wasn't happy.
Where am I coming from? Start a special engine savings account or start buying parts as you can afford them and set them aside. New heads, cam, RR's, throttle body,etc. Save for them or buy and set aside.
When you are ready buy that used block (mine was $100) and stroker crank and let the machining begin. Assemble your new 408 and when that weekend comes....swap out that stock 5.9 that you saved thousands on not modding and swap it out.
I am sure many on here will tell you it can be dissapointing after spending big ...and finding out how little your 5.9 changed. Save for it and you will not be dissapointed. The 408 will change your truck big time and will give you far more bang for your buck. I wasted a lot of coin....don't you!

 

Lol I agree with the mode I have done I want it like the newer trucks that are up to date with good power from factory

 

I have spent 3K on my truck since 2008 (counting oil changes, tranny fluid change, etc), and it runs beautifully.

WHere people break things is modding an engine with 150K+ miles on it NOT KNOWING that the block is garbage. I know because I put high compression heads and a ridiculous cam into a 1986 IROC that had probably been run hot one too many times. It had blow by and the higher compression just made matters worse.

The thread should be changed to "Only mod a 5.9 in good condition."

But I agree, if you have a spare block, just work on that for about 2 years, saving money and just do a swap when done....hopefully the rest of the truck is still good by then. Because you will NEVER get your money back for all those parts.

 

at least the mods i have done are good to go on the 408 like the intake maniold and my longtubes and 1.7 and 14x3 and sct tuner ... not like i went internal in my motor too mod it... maybe someday i will do a 408 .

 

in my opinion all a stock engine needs a better cam and your good to go. the first thing i plan on doing to the engine in my 81 is the cam.

 

Yeah, dont mod that 360...Because everyone knows that the 318 is the better engine!

 

Moparman about how much and how long did it take you to save up for a 408? Did you buy all you parts new or did you find some decent used ones?

 

1996 5.9 block..................$100
rods and pistons..with block....25
Scat crank.........................350
Icon forg. pistons................400
Big valve R/T heads(used).....700
1.7 RR's.............................400
Holley 52 tb........................400
Machine block.....................650
Balance.............................250
new Harm.Balancer...............250
$3525...assembled.

My son assembled the engine, notched block, polished up and gasket matched intake. We also (after wear measure) used my 5.9 cam. We also had to purchase 30lb injectors($300) and spent $650 B&G tune.
I bought all the parts bit by bit and cheated as I did use them on my 5.9.
Engine is running on 94 octane with 10.5 compression. We felt bumping up compression was a cheap way to grab some extra horses.

 

So hows it run lol

 

Forgot to mention we bought the pistons and rods with 96 block as we also used the stock magnum rods. My son has built a number of small and big block Mopar strokers and said the stock rods have a good reputation for being tough. He was much more confident with these than some products now being made in China and the engine was not going to be run into the 6000 rpm area.
The engine now has 5000 kilometers on it. We had some lean issues at start up but after an injector change it is running strong. Best money I have ever spent on truck! We can move to a computer friendly cam in the future if we so desire.
The used R/T heads came off a Mopar crate engine (only had 3 to 5 runs on strip with them). Friend immediately went to aluminum Magnum heads.