I have located a GMC engine.The only ID I could find was a L86/NA5 number and it is of the GAR family.The engine was in a 1981 school bus. It also indicated that it is a big block 366 cubic inch and to use 91 octane or higher. I would like to know if this engine has a steel crank and if I could convert it to 427 cubic inches by changing the rod lengths. I would like to use this engine for a marine application or 1/4 mile
drag car. Any info in on this engine would be greatly appreciated, since it is running and almost a freebee.