Failing that, if you're more focused on a Petrol car, get an old Civic (1990's, 1998 is particularly win.) with a Vtec in it, they're not expensive cars (Read: Insurance may be) but you can get good strong 1.6 VTEC engines that'll rev and rev and rev.
I take no responsibility for you killing yourself
But converting an old Fiesta from Diesel to Petrol strikes me as a waste of time, you'd be better doing as HDi mentioned
Ta!