I have the same '98 Anniversary ProStar as Captain Planet with the 350hp LT-1, but we also have the Power Slot transmission. No regrets as the boat flat out rips compared to our old '85 S&S with the 1:1. The LT-1 is definitely the way to go, no downsides in my eyes. I thought with an additional 100 hp to feed (compared to the 351w) and the Power Slot the fuel consumption would be poor. But the fuel consumption ( with 4-6 people in the boat on avg, tower and heavy subwoofers up front) has been better than the '85 was with just 2 people in the boat.
The '98 had been a win win and we love the roomier interior space. Hold out for the right boat and the LT-1 or you will always want one wondering what it would have been like.