Making ignition harness

I have IO-540-C4B5 with dual Bendix SL6 series 200 mags. I need new harnesses for both mags.
I see ACS sells a kit to make your own harness. I have never done this nor seen it done. It is much cheaper than buying complete ready to install harness.
Link to mentioned kit: http://www.aircraftspruce.com/catalog/eppages/shieldedharness.php

I would like to know how doable this is? Worth doing it vs buying ready made kit?
Also, what is the most commonly used spark plug -harness connector size? 5/8 vs 3/4.

This is a ready made kit, more expensive: http://www.aircraftspruce.com/catalog/stpages/slickharn_08-08653.php?clickkey=329149

Any other options?
Thanks.
Johan

I am all for building your own harness and would love to do so on my Slicks if I could. However, be warned, I bought an ACS harness (same Mfg and same blue wires as the one in your link) from aircraft spruce for my rebuilt O-320 (complete harness, not build yourself). At 10 hours I pulled the plugs to check them. On approximately 4 of the 8 wires, the Ceramic/Composite sleeves on the plug end were cracked lengthwise and separated in two. While in theory they could still be used if you didn't drop one of the two pieces, they were scrape. ACS, the OEM, not Aircraft Spruce, would not honor a warranty claim as they were purchased over 6 months earlier. I pressed Aircraft Spruce pretty hard and they ultimately gave me a full credit.

In my opinion, they used a very cheap and un-suitable substance for the sleeve instead of a nice piece of rubber coated material as typically seen in that part.

Just thought I would share my experience.

Larry

Built one for the first time. Went slow, did very careful work. Seems to be working fine. Seems some race through things they've never done before and end up with problems. You can check them after to see how you did.
Bought that P-mag from a guy that couldn't get it to work. Went slow, did everything carefully per the instructions. Works fine....new harness too.

Make your own harness & convert to auto plugs

Measure the total length of plug lead wire you need.
Buy a bulk roll of MSD superconductor 8.5mm wire, and 12 plug boots.
Many 6 cylinder Bendix mags have lead plates with thread in gland nuts that hold the wires (think distributor cap). I have the same on my 4 cylinder mag. The MSD wire fits this plate. Insert a pop rivet (without the pull nail) or small screw in the end of each wire to make a good contact to the mag lead terminals.
Use the 18mm -to- 14mm spark plug adapters and NGK BR8ES spark plugs.
Gap the plugs to 016", same as the published gap of the aircraft plug.
If you have press together mag plate (not the gland nut type) you would need to modify the plate www.g3ignition.com/ sells instructions to do this for about $30.