New truck, or new torque conv/tranny?

I've got a '99 Silverado w/5.3L that's got over 75k miles. It's been through a fair amount of towing an approx 6,000lb car/trailer combo.
I want to get an enclosed trailer, which I know will be stressing the limits of the current powertrain, even if it were new.
Is it worth considering upgrading the TC/tranny, or should I save my money for a new(er) truck?
I'd really like a 6.0L Suburban/Yukon XL, but I don't know if I'd be doing myself any favors with that combo either.
And as bad as I want a diesel, I just don't race THAT MUCH these days, and the SEDIV is pretty flat.

Thanks,
Michael

Michael,

How much would the new trailer weigh? I think you're already at the limit of what that combo can handle. I used to tow a 20' enclosed trailer approx. 7K lbs with a 99 1/2 Suburban (350cid). At 53K miles, I had to put in a new diff and axles.

A lot more important than going is stopping, I think you'd be way better off w/ a 3/4 ton, just from the brakes point of view.

Michael,
You might want to talk to Tim B. I think he wants to sell his big diesel. The price was pretty reasonable. Let me know if you need his number.

Jim

I'm not too worried about brakes since the enclosed would have dual-axle brakes. My current trailer only has single-axle and it stops pretty good. I'm guessing my loaded enclosed would weigh 8,000lbs, which just happens to be the max recommended for my truck.

Thanks Jim, I'll shoot him a message.