Bolt on bellhousing. AX15, AR5, MA5, R154 all have the same face, so if you can find a bell that fits your motor you are golden (for the most part). That's why a Toyota Supra R154 can be bolted up to a SBM.
There used to be a huge thread about swapping the R154 and it's brethren, I think on Jeep forum? Haven't looked for it for years though.