Find either set of 243/799 and just bolt them on, The compression will go either way. By the time you buy heads you find, mill them, order pushrod's, install valve springs, then P&P the heads, pay for any machine work and labor you could buy a decent set of aftermarket heads for the money that you will spend working stock castings. If it were me I would just find decent set of stock heads, change the valve springs and stem seals, clean them up and bolt them on until I was ready for a good use of CNC'd units, or until I outflowed the stockers...JMO