This is not an easy job fella just to give you an indication what’s involved I'll run down some info.
Heavy duty valve springs
New tappets (optional)
Upper to lower intake manifold gasket
Replacement ECU chip
Lightened balanced flywheel
Removing cam sprockets
Tools:
Valve spring compressor
Cam alignment tool
Holding valves closed while springs are removed via compressed air whilst poking around in a spark plug hole trying to pick the dam things up!
Plus only limiting yourself to the extra lift without ported manifold for quicker compression is a waste IMO.
That’s just a tip of an iceberg for 15BHP for money?

Ring a company that does this sort of thing to get a pro run down of what you want from your 8V there might be cheaper way to getting an extra 15BHP.
J