To some extent, you can debug a 64-bit dump of a 32-bit process with Windbg, by use of the wow64exts. However if possible I think it’s best to have a 32 bits dump. If the customer can provide a 32-bit dump , get it.
Here is a sample of the wow64exts:
0:008> k
Child-SP RetAddr Call Site
00000000`0291f128 00000000`779d263a wow64cpu!CpupSyscallStub+0x2
00000000`0291f130 00000000`7792c4f6 wow64cpu!WaitForMultipleObjects32+0x1d
00000000`0291f1e0 00000000`7792b8f5 wow64!RunCpuSimulation+0xa
00000000`0291f230 000007fe`e51fd6af wow64!Wow64LdrpInitialize+0x435
00000000`0291f770 000007fe`e519c1ae ntdll!_LdrpInitialize+0xde
00000000`0291f7e0 00000000`00000000 ntdll!LdrInitializeThunk+0xe
0:008> .load wow64exts
0:008> !sw
Switched to 32bit mode
0:008:x86> k
ChildEBP RetAddr
02a1f2dc 7783c752 ntdll_779e0000!NtWaitForMultipleObjects+0xc
02a1f460 75b956c0 KERNELBASE!WaitForMultipleObjectsEx+0x10b
02a1f4d4 75b9586a kernel32!WerpReportFaultInternal+0x1c4
02a1f4e8 75b67828 kernel32!WerpReportFault+0x6d
02a1f4f4 778c07c4 kernel32!BasepReportFault+0x19