Tranny linkage help

The large lever on the transmission that the stock shifter linkage slides into has a welded extension. The car does not manually shift right. I bought a used arm at the nats and will install tomorrow. Is there a proper way to adjust the linkage? I had my brother start in park and work the shifter down to first and then tightened the bolt to the proper length on shifter rod or so I thought. I have park. Reverse is either reverse or nuetral. Drive only works all the way down in first. Any ideas?