does a 904 slant torque converter=904 sb torque converter?

Yes, the /6 convertor should work with the V8 transmission since they are both 904's. Now a TC for a 904 will not work with a 727 and vice versa because the input shaft spline is different. Flex plate should also interchange as long as the number of crankshaft bolts are the same. I think most cranks use 6, but some have 8. As for weights, the /6 and 318 do not use any on the converter. I recommend using new bolts for both the flex plate to crankshaft and the TC to flex plate.