OldIHC

I am looking to get 20km more per hour out of my L130 to bring it up to 80km/hr. I am wondering what the best method is to get there.

Find a nice long hill with a straight road. Hope for little or no traffic. start the decent put the clutch in and hang on. The original brakes are not likely to slow your nearly out of control thrill ride.
I have modified a few of these old IHC trucks. An IHC 304 V8 will bolt right in and suddenly there is the speed you are looking for. If something gets in front of your truck, the brakes will not stop or slow your truck.
What Old IHC built was a not too bad package that included brakes and a top speed that are compatible.
If you want to go faster, you need to stop more quickly. The OEM brakes are not able to convert the kinetic energy of speed into stopping power because of over heating. The design of the brakes cannot cool quickly enough.
If you modify any part of the original engineered package and there is a life threatening injury or fatal from the collision caused by your modifications, you may be held criminally and civilly liable and be paying for damages for the rest of your life.
There are few things to consider.

^^^^^^ I agree, when it comes to old trucks I enjoy life in the slow lane. I am lucky to live in a rural area and not have to deal with four lanes or free ways, just country roads when I drive my old iron. Years back I did have a fifty Chevy that I restored but built out the motor somewhat and changed the rear axle gear ratio to allow it to run at modern speeds. The first thing I did though was convert the front brakes to discs to handle the extra speed. I sold it and any old truck I've had since then hasn't seen speeds any faster than 45 mph.

Thanks both for your honest relplies. Cool and slow is how it will be. Moving the tin to a new platform to me makes it a different truck and a deviation from how things were back in the day.

Drove the truck home 2 hours when i bought it last week. Lots of thimbs up from the front and an equal amount of fingers up from behind!

Truck should be able to do 80Km/h stock, and stop as well. My earlier and heavyer K-7 will do that stock.
There are plenty of things to check out before changing any thing.
Start by going thru the brakes and making sure there good, check tie rods and drag link to make sure you can steer it.
On the engine check timing, static, mechanical and vacuum advance curves then move on to carburation.
80-100 km/h should be do-able safely with a stock truck. 100 being the upper limit. depending on tires and gearing you may be pushing the upper limit of the engine RPM around 3200.

80 kph equals 50 mph.
Your L130 should be able to go 50 mph easily when new and now.
How about:
some photos of the truck,
engine info: size, ignition, carb,
trans info: forward speeds, column shift or floor shift, etc.
axle ratio,
tire size,
4x4 or 4x2,
etc.

My L112 could do 50 and a bit more if it had to but the way it was geared it was much happier out on the highway going 45. That was the sweet spot for that truck and it would lope along all day at that speed. Another 5mph above that and the whole truck felt stressed out.

Just about 28 years ago I gave in to need for speed and better highway manners. I had a road slug 1953 R120. After a few years of holding up traffic, my wife suggested that we make the truck reliable and make it run and keep up with traffic.
The details of this rebuild of a restored truck are long and boring and on this forum somewhere.
To shorten the agony of TMI I installed an IHC. 6.9 Diesel V8 and a C6 automatic. The "R" became a 4X4 with Dana 60 axles and four wheel disc brakes. Gearvendors Overdrive made the maximum 4000 RPM Diesel from 60 MPH to about 90 MPH. This combination lasted for 20 years and 225,000 miles with nothing more than regular maintenance.
Did I lean anything? YES! 1) A Cummins would have been a better choice. 1a) to make the 6.9 fit, the firewall required major surgery. 2) Be prepared to spend money. I did all of the work in my shop. I had to spend $26,000 for everything I needed and did not have. 3) There is no shortcut so success. 4) The old 6.9 is a lazy lump of iron. the fuel economy was really good at nearly 30 mpg on the highway and 20 mpg in town. This 1150 pound engine was underpowered on mountain roads between here and Alberta.
I got the finished truck inspected and it passed. My best effort to build a truck was approved and the rest is history.
Hundreds of times or maybe many more, I enjoyed starting the 6.9 Diesel and watching for the surprrised looks of those who did not know the truck.

What rear end does your 130 have? My L110 will easily do 50mph.

The 130 had these rear end ratios. Axle Reductions: 4.3 to 1; 4.88 to 1; 5.571 to 1; or 6.166 to 1.
The 110 had these axle ratios. 3:73 and 4:11
While your 110 may go as fast at 50 mph with the 3:73 and maybe struggle with the 4:11, it is unlikely a 130 will be able to do the same speed with the axle ratios available in the 130.
From this bit of information you can see there no ratio overlap for comparison.