I thought my cruiser had a bad thunderbolt yesterday. I swapped the ignition from the good engine and she fired right up. Well before ordering one today I told the story to some good friends and they said it could have been a bad connection. They were all tight and looked fine but I crimped on 5 new ring terminals and re installed and she runs like a dream. Went out yesterday and today zero issues.

Try new connections before wasting money.

I appreciate the information. I did find loose connections in the main engine harness. I opened up the pins and checked voltage at various points. That's when I noticed the module had it's locking tab broken off. I have some lines on a module or two, but I feel without a locking tab it'll loosen up.

the 20 will work just fine just set your timing at total advance. You will need and advancing timing light so you can set at full advance.

I have a digital Bluepoint timing light, thanks.

the v6 modual is the cats ass you can run more inital timing

^^^Even for a stock 260hp 5.7?^^^

I plan on installing an Eddy intake and possibly a 350 Mag cam in the off season.

Here are the advance curves for all the modules. You don't want a V8-20R unless you plan on running the engine over 5300rpms.
Will it work...Yes. Should you use it...No. It will never fully advance.
You want to use a module that has full advance in by 4000rpms.

we use the delco est system to replace merc thunderbolt more reliable and hotter the secret for fishermen is it idles at 18-20 degrees so its very quiet and very smooth for hours of trolling the v6 box gives more inital if you set the top end timing to 30 at 3500