You don't want a Hyper-Pak in a heavy truck. It's made to run in a narrow, high RPM range more suited to light vehicles and racing.
If it's equipped with a 1-BBL now, a Super Six (2-bbl) will make a big improvement in torque and midrange power, which is what you need in that big crewcab. Plus, if you get all the parts (see Reed's excellent Super Six article in the articles section) then it's a bolt-in deal for the most part.
Milling the head to increase compression will help. Don't bore for power. If it doesn't need to go that big, then save yourself the overbores for future rebuilds.
The exhaust will help a great deal over stock.
Check the timing and make sure you have 30-32 degrees total mechanical (vacuum disconnected). Turn the rotor against the spring and make sure it snaps back easily and fully. This will affect some of your starting and idling problems if it doesn't. If this is the case, you'll need to put a rebuild on that distributor. Electronic ignition will help.
Hope this helps.
Edit: I checked your pics. That is one sweet Sweptline. I'm a Sweptline owner myself, in the form of a '70 D300 tow truck with 46,000 original miles on it. Sure would like a crewcab though... 
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New guy here, I have a 225/6 premium engine in a 1969 W200 CrewCab ex USAF truck and am very frustrated as my engine is making less and less power (won't even pull in 4th gear now) won't idle and is extremely hard to start unless I "pressurize" the fuel tank. It only gets worse after truck has warmed up. I have replaced the fuel pump, and the coil; to no avail. On my way to NAPA for a carb kit, and am ordering a Pertonix electronic ignition. The distributor is all the way advanced and only runs worse if i retard timing, making me suspect a stretched timing chain could be culprit. Anybody have any ideas?? I need to get this figured out or will likely drop a 318 in truck, as I just sold my other truck and now need to use this one for a daily driver...HELP!! -Spin
OK Doc, did compression check and the results were none too encouraging, here goes: 55 85 0! 90 40 30.....did a quick adjust on the valves (.012 int .022 exh) a few of the exhaust valves were tight (seat recession?) any way; the numbers evened out some: 50 80 40! 75 50 42.....should get carb back from rebuilder tomm. I suspect I have a ring problem as well as a tired head. What say you?
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