You could buy the K5 blazer. Drive it. Buy a Cummins 4BT diesel later. Then install the Cummins 4 cyclinder when you are ready. They make bell housing adaptors to bolt the Cummins directly to the Chevy transmission. I read guys were getting over 30 mpg on this little diesel. The Cummins 4BT was in some of the older bread trucks and aluminum bodied delivery vans. Or you could go Cummins 6 cyclinder like this guy...

http://www.4btswaps.com/forum/showth...-swap-for-real!