So they weren’t lying…

You cannot use a 354 Chrysler crank in the Desoto 341 block. It is too long and will not fit in the block. Bonus is, you have a 392 instead with the best heads to use. You can sometimes find Desoto 330, 341, or 345 cranks for sale, any of the 3 will work.
Good to know! Thanks! It would’ve been really cool if the 341 was a 354 but like you said, beings the other one is a 392,I have the good heads AND it was all free, I’m perfectly fine with it being a 341! A 354 would’ve just been extra icing on the cake! Lol