If you dont feel quailifed to do it yourself, any decent machine shop can machine your current heads and install differant springs that increase the clearance,
but heres a cheap way out PROVIDED YOU TAKE THE TIME AND EFFORT to MEASURE eveything and VERIFY you have the necessary clearances, which you should have and because you only need about .020 more lift/clearance.
THESE ARE NOT THE CORRECT PART NUMBER
swapping valve locks for ones designed to increase the installed height .050 taller should solve the clearance problem, but be aware theres a possiability that longer pushrods will also be necessary to maintain the valve train geometry
the valve locjks can usually be installed with the heads still installed on the engine and with the engine IN the car
youll need one of these tools (rent or buy one)
FOR SAFETY REMOVE THE BATTERY FIRST!!
youll need one very similar, tool, you remove the rocker arm,s from the cylinder youll work on,next
you remove the spark plug and insert the threaded air adapter in its place,threaded on the rocker stud, pressurize the cylinder with 130 psi to keep the valve closed
screw the tool on as far as you can, align the twin fingers so the valve stem and keepers can slide thru, smack the keepers and spring retainer with a plastic hammer after spraying lightly with a few drops of carb cleaner to make removal easier, place several STRONG magnets around the spring to catch the valve spring locks/keepers if you get careless to prevent them getting away or lost or into the engine, pull the handle to depress the spring, the old locks should be easily picked off, the new locks replaced in thier place and they are installed. let the handle up yeah ITS far easier than it sounds and after you do a few dozen engines it becomes even easier...BTW if you don,t have a decent compressor, run the cylinder down to bdc by hand DONT USE THE STARTER, YOU SHOULD HAVE REMOVED THE BATTERY
remove the spark plug and insert about 8 feet of 3/8" cotton rope into the plug hole , it will coil up(don,t forget too tie a big knot in one end so it can,t all slide in if your dumb...MANUALLY WITH A BREAKER BAR,crank the engine to tdc or as close as you can with the rope pressed against the valves, ...remove the locks/retainers, replace with new, back off the piston, remove the rope and move to the next cylinder