Cubecart migration 3 -> 4 with custom mods

We currently run 2 identical shops in Cubecart 3.0.17 heavily modded. We need to upgrad them to the latest V4. Somemods can be bought and need to be installed, others ned to be rewritten to fit V4 coding. There will be no design work required, pure migation and modification. We are looking for a reliable source that has previous Cubecart experience as we need to have a quick turnaround time. We are in the process of preparing th requirements definition and unserstand that at this point all pricing will be indicative as the whole amount of work involved is not clear yet. In addition there will be a follow on poject with further enhancements, so a successful compltion will lead to additiional work. Modifications required: All in one shipping (Estelle's mod) Payment by Country - custom written to allow/block payment gateways by client country Featured Product, same mod as currently used, with Images so we can promote specfic products Related Product - (several available, so us 3rd party and install it) Payment Reminder e-mail - (custom mod o send a reminder i paymnt hasn'tbeen made after 21 days) Tracking Delivery - ( needs analysis as now a feaure in V4, currently we enter tracking numbers where we send by registered mail) Coupon Manager - ( needs analysis as now a feaure in V4, currently we use 3rd Party)