One option is Long Rod, however; you have a lot of options on how to build a 250CC Honda engine, again; thinking "outside the box"....different brand pistons with different WristPin locations, different brand Rods & Rod Lengths. Modified Crankshafts & Pistons to Properly Clear...on and on.Korldickens, sorry for derailing your thread again.
If I put a 130.50mm long rod in my 1983 125.50mm short rod motor which has 1.50mm piston edge below deck. The piston would be 3.50mm above deck.
If I put a TRX piston in my motor on the long rod the piston would only be 0.30mm above deck on the '83 motor. Reason is the TRX piston pin is 3.20mm higher towards the crown edge.
41.20mm 1983 pin center to edge
-38.00mm TRX pin center to edge.
Both pistons are identical in height.
So a standard .020" base gasket 0.30mm thicker (0.032")would bring the piston to zero.
BDT Has built a lot of engines "outside the box" or normal; like; de-stroked & Bored 250CC to 198CC like the Old-school 200R, a New Modern day 200R with Square Bore & Stroke mimicking Team Honda's factory 200R in 85-86...just about anything is possible...with ingenuity, skill and the right resources.