273 auto trying to find the 'tick'

HellooooFABO!
I have a friend who has a 67 fastback and experienced a 'tick'. it seemingly was coming from the back of the motor/trans area (auto). He has pulled the trans and wants to start the engine to narrow it down to it being the trans.. or engine. He wants me to build a bracket to hold the starter and then plans on putting a flywheel on it that he borrowed. Im not sure he has the proper flywheel, I think it may be a truck one but I havent been doing mopar stuff long enough to know. I have a /6 flywheel. His converter is 122 tooth. I have a small block bell but he for some reason didnt want to mount it for this. Im kinda following on this one, but Id like to know if the /6 flywheel will work. Im in the market to get a flywheel for a 360 I have lying around, but with shipping and tracking one down used the timeline is not lining up. Just spit ballin....any ideas? Im probably missing something easy here.

Thanks!
Clem

We think its the converter....but just a guess.