is the jump pack now charged by the alternator like a standard car battery would, if so it may not last too long as I have had jump packs last for years as long as I removed the charging kit as soon as it was full, I have also had jump packs last only months if I left them on a continuous charge..... not sure if it is coincidence, but that is my experience, I sure would be glad to hear what your experiment yields.

If the voltage coming out of the jump pack battery's charger is nearly the same as the charging voltage from your alternator charging shouldn't be an issue.

The only big difference I can think of off the top of my head would be resistance to movement and sloshing. The race battery may have had more acceleration resistance built into it than the jump pack battery.