engine question

[hobsiscool]

Ok...I think i'm kinda leaning toward building the inline, however i'm still having some trouble figuring out which head I need to get...if someone has pictures or can point me to an ebay auction, etc of one, that would be awesome...second, before I can do any of that, I need to figure out what's going on with my engine...I'm about to take it in to get looked at, but it would be nice to get some ideas here...it runs fine, idles fine, it just makes a loud clacking noise and smokes...what could this be??

Also, will a TH350 bolt up to my engine without any modifications?

Thanks guys