I have a 1974 Ford High Boy with a 428 motor. It currently has a stock 4 speed transmission. I am wondering if there is a 5 speed transmission out there that I can convert to? Also, who makes it and how hard it is to change it out.  

You can put a 5-speed from a 90's 1 ton ford in it.I'm not sure how hard it would be.But the tranny will handle it since ford put them behind 460 big blocks.  

Thanks. I will look into that.  

I havn't seen your tranny but it is probably a NP 435 which is arguably the best manual tranny ever built or it could be one of the Borg Warners that i have seen but I havnt seen many If it is the NP 435 i would leave it alone unless you just have to have the high gear  

On the 5 speed from the 460 in the newer truck it has a aluminum case and rated for 450 ftlb torque max. I was looking into one last week for a 400 ford and think it will work for my situation. But the 4 speed you have is a tough piece. They make a overdrive unit that bolts to the rear of 205 and give you another gear but will not work in 4wd when going down the highway. Believe its gearvendors or something like that. My buddy lindsey has one on his 460 ford with c-6 auto/205.