MY6 is a drop in fit to replace a saganaw.
Not exactly true. The transmission or the bellhousing will need machining to bolt together. The bellhousing of a 235 is indexed to 4.686 inches. The bearing retainer of the MY6 is 5.125 inches. To get the transmission to fit the bellhousing, either the bearing retainer has to be turned down to fit the bellhousing, or the bellhousing needs to be bored out to fit the bearing retainer.
Of course if you use the dodge version of this transmission, you can simply use a 1 inch adapter plate that goes from the chevy pattern to the dodge pattern. The Dodge version of this transmission has a pilot shaft that is 1 inch longer allowing for this unique conversion.
If the stock rear end is in good shape, there is no reason to change gear ratio. The 3.90 ratio will be like a 2.85:1 in overdrive. I wouldn't expect a mild 235 to be efficient or peppy with a higher ratio.
