about the gearbox , im also using the F5M21 iswara gearbox with the 4G63 engine , its been 8 to 9 months , and looks fine to me . the 9" flywheel & clutch won't fit in unless you skim ur clutch cover or either skim the gb housing . but its better to skim the gb housing .
why im using the 1.3 gearbox ? cause is lighter , easy to take out , and no need to modify the driveshaft , if driveshaft patah can go buy a recond iswara driveshaft which is about RM 100++ . where else when using the vr4 gb its so freaking big & heavy but its strong , driveshaft need to custom or mix & match or you can do the potong sambung style which it won't last .
1.3 to 2.0 i donno can or not , but anyhow i have a spare 4G61 engine , so anything happen's i`ll swap the block .