Am looking to buy an engine to strip down and rebuild as a upgrade for the 1600 in my ghia.

Can pick up a non running sp now. Or should I wait and find a dp?

What is a better option?

Not much difference for a standard build.
If the SP is complete and the right price and you want TP change the heads.
New TP heads are not that much money and you can bet whatever core you buy will need the heads reconditioned anyway.

Some people like the SP as they give more low end driveability but will run out of puff sooner up the rev range.

Either way the exhaust guides will probably need replacing so unless you're just gonna pop it straight in as is then DP heads will be cheaper and easier to find than SP.

The plan is to build something with a lot more power. So after doing some reading I may replace the heads anyway.

If you're going to build one with ANY "more power" you need a 1600 twin port case with twin relief valves, engine number usually starting with AD. Don't even touch anything that was a 1300 or 1500 starting with H or F and their equivalent Type 3 cases. They are just clearanced 40 horse cases and don't cut it. If they aren't cracked now, after almost 60 years, they soon will be.

Already got an AD code twin port in it. Have the option to buy a single port AD code.