I've made some upgrades from stock to the vehicle over the years. A good friend gave me a 68' 340 block with the steel crank. I built that over the span of a couple of years. A garage project as I got some extra money. Mild street. After I got that topped off. I pulled the original 360 and dropped that 340 in the bay. After adding a loose converter. Also removed the 8 1/4" drum to drum differential housing. Installed an 8 3/4" drum to drum housing and added a 3.91 sure grip gear set. Another gift from a good friend. After obtaining a set of A-body sized axles with the 4 1/2" bolt pattern for the 8 3/4" housing. I was able to transfer all of my rear drum brake components from the 8 1/4" housing to the 8 3/4" housing. Man! that woke that car up. Night and Day difference. I still have all the original engine parts that I pulled out as well as the 8 1/4" axle housing with the 2.94 gear set. A real fun driver.