This is definately going to be argued, but I have no problem with a 300 6 cyl engine, though my trucks have the V-8's. Steve has one is his Bronco, and he went through the trouble to put it in, I'd say it must have been worth it.
Does fine by me. With a little work you can get big improvements in performance (intake/exhaust, cam). Mine is an 83 with a gazillion miles on it and it pulled my 68 Mustang from El Paso to Augusta, GA. no problem! Had the AC running the whole time also.
I have the 6 in mine but with alot of aftermarket parts on it, you get ok performance and alot of torqe stock.
If you want to build it up I would change to a 351 or bigger the 302 is weaker than the 300, and the parts for a v8 are cheaper and easer to find and more to choose from.
I realy like the power my 300 has after the performance parts but it cost alot to get there 2000$
go to http://www.broncograveyard.com/ they have kits to put a v8 in your bronco like a 351 ar a nice 460 plus lots of other parts and they have good prices.
I have no history involving Bronco's until I purchased my current hunting vehicle for only $1000.
It didn't run at the time, and I have had to learn as I go involving maintenance and such. I have had a problem as far as getting parts for the vehicle (Pepboys, Autozone, Oreilly's, Carquest, Napa, LMC, BroncoGraveYard, and Ebay) but the problem is only that the stores didn't have the parts in-stock. I have had to wait for as much as a week to get parts in. The longest I had to wait was for a K&N Filter, purchased from Autozone (which had to ship from Dallas).
Over time several people make the comment saying "I didn't think they put engines that small in those", and most folks are asking "Where did you find this? You got the best engine that was ever put into a Bronco due to Torque and Gas Mileage". I've never had experience with the 302 or higher engines w/V8's but so far I'm impressed with this I6.
the 300-6 is a great motor. they run for ever and have great low end. i have a 5.8 in mine now but was originally a 302 so the upgrade was for sure needed. but had there been a 300-6 i would have kept that motor in for sure.
I love the 300. I searched for a 300/5 speed specifically because of the reliability. My dad had an old Ford F-150 with the 300 in it and at over 300k miles it still ran awesome, only thing he had to replace in 4 years of owning it was the alt. My best MPG to date is 16.08, I'd say it averages 15.6 which is damn good.
I had the I6 great running motor, hard to kill unless you heat it up like I did to mine. I just happened to have a 429 in the shed so that went in. Me personally I am more happy with the power of the 429. With 38.5 swampers in the mud it was a little bit of a struggle to spin the tires in 4 low. With the 429 it is no problem.