I just picked up a 1990 that I know little or nothing about the L98 other than it looks to be all original. The previous owner installed a DUI HEI Distributor and a MSD 6AL . The Wiring looks sketchy at best and the 6AL is just laying loose its never been mounted anywhere. Its got a couple of Home Depot mounting brackets and looks as though It might of been pulled from one of his other cars at the last minute. He had a number of drag race cars. Anyway I'm not so sure I really even need a MSD on what I think is a stock L98 but if it works Ok where have You guys found to mount it ?

 

That is going to be a "On-Site" decision as only you are going to make after finding space around the engine and controls in your 1990. The MSD 6 Boxes should get a set of isolation mounts and find a place out of the way without any potential for electrical noise. I have used these MSD Boxes for decades and love them. If you can find a place out of the way and Fairly Flat you can make it work.
It turns out that Summit now offers their own version for $11.00:

Summit Racing SUM-850112 - Summit Racing® Vibration Mount Kits

I never put one on the 1988 C4 i have because the HEI is a coil setup from the Davis Unified Ignition Company and it makes a "nasty" HOT spark all by itself. I am not sure what benefits or gains they were "expecting" to justify mounting a MSD 6AL on a Fairly-Modern Computer Controlled Engine. The newer factory style ignitions are getting better, But I don't think they have adapted the multi-spark concept that MSD uses, yet. I might be wrong with the newer super clean running engines that have out there.

Independent ignition systems were great in the old days but my Holley EFI system will control both Ignition and Fueling of the engine allowing it better control of the engine.

I might suggest that for simplicity's sake that you would remove or undo the MSD system and get it running the original way. Your factory ignition is pretty darn good for it's day. A good cap with a good quality coil along with a new set of spark plugs and wires makes a "very happy" performance HEI system. The factory system at the time in 1988 is "okay", if not, even "pretty decent". I wish I had some of the nicer features "standard" on the 1988 C4 ignition in my older C3 Corvette especially knock detection and timing corrections that follow....

Best regards
Chris

P.S. IF you don't have a Factory Service Manual set for your Corvette then you should get one as they are "priceless" when working on your Corvette. They have detail and trouble shooting tips only a manufacturer could make. They sell them in hard copy at Helms Publishing for about ~$100 and the DVD's are available on Rockuto for in the low to mid $30.00 range. Whichever suites you better but it is really helpful getting your Corvette back in action.

 

OP - I've PM'd you an interesting FSM offering. For a '90 I have both 'RED COVER' PAPER available as well as other interesting information for '90 model year!

 

 

I put a 6AL in my 86 in the little cubby behind the drivers seat right above the ABS unit. Keeps it safe and dry. It has been working great there for the last 3 years.

 

I suggest that you take WVZR-1 up on his offer. I did in the past. He is an honorable forum member to deal with.