The Thunderbolt ignition is really a great marine ignition system. All you have to do is replace the distributor pick up's and caps every 2-3 years. We raced with the standard Thunderbolt IV for 10+ years and never had a any issues. They should perform flawlessly to minimum of 6000 RPM.
IMO, the MSD system is a step backward in performance and reliability.
Ben

I replaced mine with HEI marine units. So far so good.

Last 5 yrs. ran the DUI w/o a burb. Call them and they set up the timing on dist. for your application. Best dist. out there.

Pulled the t-bolt IV from my 7.4/330 and used it with my ZZ502 for 4 years. Now it's in my 557ci along with a Crane box. Engine runs like a top.