The Related Products Import module imports product codes
of the primary products and their related products from a
flat file.
Easily create a flat
file of your products and their related products, then
import that file's data directly into your new 4.x store.
It verifies the existance of products before linking
them, thus preventing double entries for the same product
or linking of products which do not exist in your store.
No related products import would be complete without a
related product export module.
We also have the corresponding module for the 5.x version of Merchant.