How to tell gcc to not align function parameters on the stack?

I am trying to decompile an executable for the 68000 processor into C code, replacing the original subroutines with C functions one by one.

The problem I faced is that I don't know how to make gcc use the calling convention that matches the one used in the original program. I need the parameters on the stack to be packed, not aligned.

Let's say we have the following function

int fun(char arg1, short arg2, int arg3) {    return arg1 + arg2 + arg3;}

If we compile it with

gcc -m68000 -Os -fomit-frame-pointer -S source.c

we get the following output

fun:    move.b 7(%sp),%d0    ext.w %d0    move.w 10(%sp),%a0    lea (%a0,%d0.w),%a0    move.l %a0,%d0    add.l 12(%sp),%d0    rts

As we can see, the compiler assumed that parameters have addresses 7(%sp), 10(%sp) and 12(%sp):

but to work with the original program they need to have addresses 4(%sp), 5(%sp) and 7(%sp):

One possible solution is to write the function in the following way (the processor is big-endian):

int fun(int bytes4to7, int bytes8to11) {    char arg1 = bytes4to7>>24;    short arg2 = (bytes4to7>>8)&0xffff;    int arg3 = ((bytes4to7&0xff)<<24) | (bytes8to11>>8);    return arg1 + arg2 + arg3;}

However, the code looks messy, and I was wondering: is there a way to both keep the code clean and achieve the desired result?