It's a fairly clean swap and IMO well worth the effort ~ the front timing cover will need t be swapped from the 216 to the 235, this involves two bolts _inside_ the sump being accessed, man take the time to drill these threads out .
Please take the time to look in the older threads as this has been covered in detail many times over if 20 + years ago .
Some thoughts on the engine you choose : all 1955 > 235's are good but the later model you get the better they are, particularly the top end oiling and cylinder head castings .
They're still plentiful if you look ~ most who have made a Hot Rod still have the old 235 take out sitting in or behind their garage and have given up trying to sell them, often they'll give them to you just to be rid of it or will sell for under $300, I'd never pay over scrap value for one, the raised casted number on the forward left side of the cylinder head will hopefully end in 050, that's the last and best casting .
Of course, there are still millions of better, 261 C.I.D. engines out there in 1 ton and larger Chevy trucks from 1955 ~ 1962, mid West junkyards have them by the score, I know a fellow in Kansas (Hutchins, IIRC) who sells them all the time .
Typically if they turn they'll run, then you can easily nurse them back to robust health without needing total rebuild .
Of course, if you're rich you can buy them fully rebuilt from JASPER Engines in....?Colorado? .
Please keep us posted on how this all goes .
Myself I prefer to keep them 6 volts, getting the generator and regulator from a '54 Pontiac with give you plenty of current to work everything, I use LED bulbs to make them light up like 12 volts .
