I can't tell you exactly, but I can warn you that its going to be expensive. The 3.7 engine was built by Mercruiser, there is very little aftermarket support for this engine and it hasn't been in production for some time. Parts were expensive when it was in production, they are probably even more so now. There are some ways to use other parts from other engines when you build one up, but its taking a "hot Rod" approach that most engine re-builders won't take due to warranty purposes. If you engine needs major work, and if the manifolds need replacing, you will probably be better off replacing it with a 4.3 V6. Big ticket items to deal with on 3.7L motors are the manifold and riser, charging system, heat exchanger, and starter. Check these components out and figure if they need replacing or upgrading. Add up the cost of these items before you start rebuilding the engine, If you're ok with the cost, the 3.7 is a good motor, it has its quirks but overall fits the need quite well, if you decide to go the 4.3V6 way, keep in mind the motor mounts to the stringers will need to be redone