Will this work for me?

You sure it's not an OD? Is the 3/4 shift lever (front one) down rather than up?

It might not bolt up, either There were some different size bearing retainers over the years and for different setups

But you can work around the retainer. When I put the 340 in my old 70 sixpack RR body, I had the bell center hole on the 340 turned out to match the original 4 speed retainer.