5 Speed in 1980 Full Size with 300-6?

Now don't laugh, I like the 300 CID In-line 6. It did just fine in an '82 F-150 that I had and figure the Bronco is a little lighter, etc. etc.

We acquired an '80 Bronco for my son and he has driven it for a couple of years. However the engine is shot, and I plan to install a new/rebuilt long block so he can reliably take it to college about 400 miles from here.

While I'm at it I'll also replace the clutch (also gone) and this would be a convenient time to swap for a 5 speed tranny to give him a little extra cruise on the freeway.

I would appreciate any suggestions for relatively easy bolt ups to the 6 cyl and the t-case. Other realistic suggestions for gaining some MPG while retaining its fairly good off-road performance would also be appreciated.

Stats: '80 Bronco Full-size, 300 CID in line 6, stock carb, stock intake and exhaust. 4 spd manual trans, 2/4hi/4lo trans case. ?? gears, assume stock.
4" lift, 33" AT type tires. Power steering, no air cond.

Thanks folks!

Apparently, your choices for 5 speeds will be either the Mazda or the ZF unit. (ZF s542) I would choose the ZF for durability. It may not matter as much if it's originally a 2 wd or 4wd since you can dissemble most trannies and change the 'tailcone' to get the other operation. (Like 2 to 4 or 4 to 2)

Since the ZF is a Borg Warner Unit, it should fit your t-case fine. (Check your part number on your T-case, to make sure it's a BW, or a NP.) You can also write Ford to get your 999 report which will list what gears you have. I did, and I found out my 4-sp NP had cruise control from the factory!!! :rawk:

Keep in mind that there are no 5 speed transmissions that will bolt up to an '80 Bronco. In 1983, they switched from mechanical to hydraulic clutches and all 5 speed trannies require the hydraulic clutch. You will have to switch out everything that the clutch uses, all the way to the pedals.
What 4 speed transmission is in there right now? There are several of those, two of them are 4 speeds with a granny gear and one of them is a 4 speed with overdrive. The overdrive version isn't as tough, but gets much better gas milage on the freeway. I have an 81 with the straight six, the four speed with overdrive, and 3.0 rear end (stock was 3.5, whoever bought mine from the lot wanted the optional 3.0), and I can get into the low low 20s in mpg on the freeway if I treat it right. If not and I'm in a hurry, I'll get about 17 - 18.
I'm looking to put the ZF 5 speed into mine sometime soon, but it will require a lot of work, as I will need to switch the entire clutch system out and scrounge junk yards for all the right parts for a hydraulic system.

Lastly, I also only have 30" tires, which helps with milage. The straight six is probably one of the best engines Ford ever made. It's got incredible amounts of torque and will last for 300,000 miles, but it's HP isn't that much. If you have a 4" lift and 33" tires, the engine is going to have to work overtime to keep them going and that might be costing you gas milage. Put a better exhaust (maybe even headers) and convert to a 2 or 4bbl carburetor so that the engine puts out enough HP to keep up with those tires.