Cheap 406 is most definately an oxymorom. I made a cheap 406 many decades ago. 1971 in Lost Wages, Nevada. Found an old 390 in a junk yard. Did some numbers checking and figured out it was a 1961/62 375 horse 390. Bought it for $100 and tore it apart. Block to the machine shop on base and had it bored .080 over(you could do that as the block were used as the early 406 blocks). Used my spare 428CJ heads and found a 406 3X2 setup complete for $200 (it's amazing what you find when you deliver parts for a parts house as a part time job). Assembled everything and had me a 406. Today the chances of doing that are nil and not at all.