I have owned several 63 chevy trucks. Each one had a 230, and I have yet to have to rebuild one. Have replaced fuel pumps, gaskets...etc..but Ive yet to need to replace a head gasket or worse. I am building a big block, but the I6 will most definitely get better gas mileage. The big block "dream" is something ive worked on for 15+ years, and finally got old enough to afford to build one....but I plan to keep the 230 and crate it for later.