fuel mileage on a high performance 350

I have a 91 GMC sierra pickup with a 305 (tbi) that the pistons recently rusted up on. Instead of rebuilding i have opted to go with a 350. I have a reputable remanufactured engine shop that offers a performance 350 with 350 horsepower. My orginal 305 got 16.3 mph. My questions are:

1. What kind of fuel milage would i be able to expect with the performance 350?

2. Would my th700-r4 transmission be able to handle it?

I also would need a chip, has anybody had experience with tbi chips ?

Thanks in advance for your advice.:D

The 350 is actually a better choice it has more cubic inches so it won't work as hard. As long as stay out of throttle you should get around 14-16 M.P.G. . The 700R-4 should give you decent cruising .I am not familiar with chips good luck.

Hey Gnob, welcome aboard, Hey, nice nick! Is that with a silent "G"? Anyways, your current system will be tasked to the gmax to supply enough fuel to the motor , even with a gputer upgrade.

As for the 700, if it is stock, you can gkiss it goodbye within a year. In the meantime, ensure that the TV cable is fully extended upon full throttle, maybe even a little gsooner than full throttle. This will give you more line pressure and extend the life of the gtranny!

As for fuel economy, sometimes more horsepower gives you better fuel economy, depending on the hp to weight ratio. Good Gluck