A wire welder (Mig Welder) is tool of choice actually for this type of work because it is less effected by direction and path issues a stick (Arc Welder) is subject to. Horizontal or vertical down is best when Arc welding and often in tight confines it is difficult to do. Also slag removal can be difficult for multiple pass welds. This type of repair should only be done by an experienced person, with a properly capable welder. You must have enough current capacity to assure the weld depth is adequate. It is also critical to properly prep the repair with grinding of frame and repair metal to V-Cut the planned weld path to increase weld depth and weld integrity. Always be safe, wear eye protection (welding mask), proper gloves and non- flammable clothing is best, leather welding jackets are a good investment. Have a fire extinguisher nearby and be sure it is charged before you begin. Be sure to disconnect battery to avoid costly electronics damage, and never weld near fuel tanks or batteries with out extra precautions. Remove battery and if necessary fuel tank removal may be the best solution to avoid any potential fire risks. You really don't want to burn down the garage when fixing a frame. Mostly because if it needs welded, is it really worth the risks? Unless your restoring a classic car, when a frame is at this stage perhaps getting another vehicle would be a better solution. Just recycle this one and use the scrap metal money to put towards the new car.