Tyically the reason 1st and 2nd feel stiff or clash is because there is still some drive going through the gearbox from the clutch and the laysheft is (consequently) not at rest.
To test this you should remove a propshaft and with the car well chocked, look at the output of the LT230.
With engine running around 1500rpm with the R380 in neutral the output should not be moving at all.
It shouldn't feel any stiffer in any direction when you try and move it by hand either.
In first, it will of course spin, however when you engage the clutch it should stop insantly and no movement should be detected as you move the gearstick between 1st and Neutral,
The same applies to second.
As long as the clutch is engaged (pressed) the output shaft of the LT230 should have no drive or torque aplied to it.
Moveing between 1st and 2nd should not offer any movement nand should be relatively slick.
If it is spinning (or feels tight) then the clutch is not full disengaging,
If that is the case then in 4th gear (straight through 1:1) would would see some movement relative to the engine speed even if you have pinned the clutch pedal to the floor.
Come back once you have complete these tests and if you still have a problem.
,that the synchro rings do not stay stuck to the gear wheels once the change has been made, so they do not disengage as such.
