A conversion will not run 10,000$ Unless you buy one turn key already done. You can get a crashed runnung 5.0 mustang for 1,000$. I wouldnt go with a chevy 350, too heavy. I heard too many stories of cracked strut towers. The 5.0 weighs only 100lbs more than the 6 cyl diesl. Put aluminum heads on it and youve only added 25 lbs to the weight of the car with a disel motor. 200 HP from a late K block should not only be easy, but reliable and pass emmisions with out any problem. And depending on what state you are in, if you put in a v-8 you may have a lot of problems getting a bar code from a smog referee