[69CST4x4SWB]

Originally Posted by Edahall

The NV5600 is one of the transmissions that will bolt up to an NP205. However, it's still much longer than the SM465 4 speed manual in your truck. That would mean making driveline changes and moving the crossmember back. You'll also need an adapter from someplace like Advanced Adapters to be able to mount it to your engine.

The other option might be to use a 6-speed ZF S6-650 manual out of a 2001 or later Chevy 4x4 truck with the 8.1L. The advantage here is it would bolt right up to your 350. However, GM didn't sell many 8.1's to begin with and finding one with a 6 speed manual is going to be even harder. Most people opted for the Duramax and Allison transmission.

Why are you interested in a 6 speed? Do you do a lot towing? If you do a lot of heavy towing, having that close ratio makes a huge difference. If you're just looking for that extra gear for better cruising, consider another option. Install 3.08 or 2.73 gears and stay with your 4 speed. My 72 Chevy 4x4 4- speed has 3.08 gears and it cruises very nicely at 75 mph.

Actually, looking for anything I can do to improve my current MPG of 8.5 as it is my daily driver right now and will be for quite a while! Of course cost in gaining MPG is also a factor. Any ideas? Already replaced ALL ignition parts which gave me 1.5 MPG gain. The Edelbrock carb (not sure of size) with manual choke seems to be working pretty good although if it sets for more than a few days, it is hard to start! As for the gears, not sure what they are either! Pretty low though since if I do a rolling stop at a stop sign, I can leave it in 3rd gear with no problem! Thanks