The 60 Caddy engine is a good engine. If it needs rebuilding you could bore it out for more cubic inches. I had a 60 Caddy limo and I agree that the brakes need upgrading.
That manual trans is very rare if original. Is it a column shift or floor shift? Three speed or four speed?
I thought that all 60 Caddys had automatic trans and a/c. Does your car have the dashboard vents?.You should be able to get the parts you need if it was removed.
Is it a two door or four door?
AL